feat(extensions): add support for local Kerberos material copy paths

- Introduced `localClientKeytabCopyPaths` and `localKrb5ConfCopyPaths` to allow copying Kerberos client keytab and krb5.conf to multiple local paths.
- Extended `BigDataExtensionsConfigLoader` and `BigDataExtensionsBuilder` to configure new paths via TOML or programmatic APIs.
- Updated `KerberosMaterialExtension` to handle file copying with path validation and overwrite support.
- Added documentation and examples for configuring new paths.
- Included unit test to validate loading of copy paths from TOML configurations.

Author: CoderYellow

doc/user-guide.adoc

@@ -1220,6 +1220,29 @@ The `KerberosMaterialExtension` publishes reusable client and service material t
 ----
 [kerberosMaterial]
 enabled = true
+localClientKeytabCopyPaths = [
+  "build/app/client.keytab",
+  "build/worker/client.keytab"
+]
+localKrb5ConfCopyPaths = [
+  "build/app/krb5.conf",
+  "build/worker/krb5.conf"
+]
+----
+
+`localClientKeytabCopyPaths` copies the same generated client keytab to multiple stable host-local paths. This is useful when several app frameworks, tools, or IDE run configurations expect their own file location. `localKrb5ConfCopyPaths` does the same for the generated client `krb5.conf`. Existing files at those destinations are overwritten.
+
+Programmatic configuration is also supported:
+
+[source,kotlin]
+----
+bigDataExtensions {
+    kerberosMaterial {
+        localClientKeytabCopyPath("build/app/client.keytab")
+        localClientKeytabCopyPath("build/worker/client.keytab")
+        localKrb5ConfCopyPath("build/app/krb5.conf")
+    }
+}
 ----
 
 Common output keys are:
@@ -1230,6 +1253,10 @@ Common output keys are:
 * `kerberos-material.client.principal`
 * `kerberos-material.client.password`
 * `kerberos-material.client.keytab`
+* `kerberos-material.client.keytab.copies`
+* `kerberos-material.client.keytab.copy.0`
+* `kerberos-material.krb5-conf.copies`
+* `kerberos-material.krb5-conf.copy.0`
 * `kerberos-material.kafka.service-name`
 * `kerberos-material.kafka.principal`
 * `kerberos-material.kafka.keytab`

extensions/src/main/kotlin/org/openprojectx/bigdata/test/extensions/config/BigDataExtensionsBuilder.kt

@@ -44,13 +44,21 @@ class BigDataExtensionsBuilder {
     }
 
     fun kerberosMaterial(id: String = "kerberos-material") {
-        extensions += KerberosMaterialExtension(id = id)
+        extensions += KerberosMaterialBuilder().apply { this.id = id }.build()
     }
 
     fun kerberosMaterial() {
         kerberosMaterial(id = "kerberos-material")
     }
 
+    fun kerberosMaterial(configure: KerberosMaterialBuilder.() -> Unit) {
+        extensions += KerberosMaterialBuilder().apply(configure).build()
+    }
+
+    fun kerberosMaterial(configure: Consumer<KerberosMaterialBuilder>) {
+        extensions += KerberosMaterialBuilder().also { configure.accept(it) }.build()
+    }
+
     fun s3Bucket(bucket: String, id: String = "s3-bucket-$bucket") {
         extensions += S3BucketExtension(id = id, bucket = bucket)
     }
@@ -185,6 +193,35 @@ class S3JceksBuilder {
         )
 }
 
+class KerberosMaterialBuilder {
+    var id: String = "kerberos-material"
+    private val localClientKeytabCopyPaths = mutableListOf<String>()
+    private val localKrb5ConfCopyPaths = mutableListOf<String>()
+
+    fun localClientKeytabCopyPath(path: String) {
+        localClientKeytabCopyPaths += path
+    }
+
+    fun localClientKeytabCopyPaths(paths: Iterable<String>) {
+        localClientKeytabCopyPaths += paths
+    }
+
+    fun localKrb5ConfCopyPath(path: String) {
+        localKrb5ConfCopyPaths += path
+    }
+
+    fun localKrb5ConfCopyPaths(paths: Iterable<String>) {
+        localKrb5ConfCopyPaths += paths
+    }
+
+    internal fun build(): KerberosMaterialExtension =
+        KerberosMaterialExtension(
+            id = id,
+            localClientKeytabCopyPaths = localClientKeytabCopyPaths.toList(),
+            localKrb5ConfCopyPaths = localKrb5ConfCopyPaths.toList(),
+        )
+}
+
 class KafkaAvroBuilder {
     var id: String = "kafka-avro-seed"
     private val topics = mutableListOf<KafkaAvroTopicSeed>()

extensions/src/main/kotlin/org/openprojectx/bigdata/test/extensions/config/BigDataExtensionsConfigLoader.kt

@@ -71,6 +71,8 @@ class BigDataExtensionsConfigLoader(
             if (config.boolean("enabled", default = true)) {
                 extensions += KerberosMaterialExtension(
                     id = config.string("id", "kerberos-material"),
+                    localClientKeytabCopyPaths = config.stringList("localClientKeytabCopyPaths"),
+                    localKrb5ConfCopyPaths = config.stringList("localKrb5ConfCopyPaths"),
                 )
             }
         }
@@ -167,6 +169,12 @@ class BigDataExtensionsConfigLoader(
     private fun JsonObject.stringMap(name: String): Map<String, String> =
         this[name]?.jsonObject?.flattenStringMap(errorPath = name).orEmpty()
 
+    private fun JsonObject.stringList(name: String): List<String> =
+        this[name]?.jsonArray?.mapIndexed { index, item ->
+            item.jsonPrimitive.contentOrNull
+                ?: error("Extension config field '$name[$index]' must be a string")
+        }.orEmpty()
+
     private fun JsonObject.flattenStringMap(prefix: String = "", errorPath: String): Map<String, String> =
         flatMap { (key, value) ->
             val outputKey = if (prefix.isBlank()) key else "$prefix.$key"

extensions/src/main/kotlin/org/openprojectx/bigdata/test/extensions/kerberos/KerberosMaterialExtension.kt

@@ -4,9 +4,14 @@ import org.openprojectx.bigdata.test.core.BigDataService
 import org.openprojectx.bigdata.test.extensions.core.BigDataExtension
 import org.openprojectx.bigdata.test.extensions.core.BigDataExtensionContext
 import org.openprojectx.bigdata.test.extensions.core.BigDataExtensionEvent
+import java.nio.file.Files
+import java.nio.file.Path
+import java.nio.file.StandardCopyOption
 
 data class KerberosMaterialExtension(
     override val id: String = "kerberos-material",
+    val localClientKeytabCopyPaths: List<String> = emptyList(),
+    val localKrb5ConfCopyPaths: List<String> = emptyList(),
 ) : BigDataExtension {
     override val requiredServices: Set<BigDataService> = setOf(BigDataService.KERBEROS)
     override val events: Set<BigDataExtensionEvent> = setOf(BigDataExtensionEvent.AFTER_KIT_START)
@@ -18,8 +23,12 @@ data class KerberosMaterialExtension(
         put(context, "krb5-conf", kerberos.property("bigdata.test.kerberos.krb5-conf"))
         put(context, "client.principal", kerberos.property("bigdata.test.kerberos.client-principal"))
         put(context, "client.password", kerberos.property("bigdata.test.kerberos.client-password"))
-        put(context, "client.keytab", kerberos.property("bigdata.test.kerberos.client-keytab"))
+        val clientKeytab = kerberos.property("bigdata.test.kerberos.client-keytab")
+        val krb5Conf = kerberos.property("bigdata.test.kerberos.krb5-conf")
+        put(context, "client.keytab", clientKeytab)
         put(context, "client.keytab.container", kerberos.property("bigdata.test.kerberos.client-keytab.container"))
+        copyMaterial(context, "client.keytab", clientKeytab, localClientKeytabCopyPaths)
+        copyMaterial(context, "krb5-conf", krb5Conf, localKrb5ConfCopyPaths)
 
         context.kit.endpoints().forEach { (service, endpoint) ->
             endpoint.properties.forEach { (key, value) ->
@@ -35,6 +44,24 @@ data class KerberosMaterialExtension(
         context.putOutput("$id.$key", value)
     }
 
+    private fun copyMaterial(
+        context: BigDataExtensionContext,
+        outputKey: String,
+        source: String,
+        destinations: List<String>,
+    ) {
+        if (destinations.isEmpty()) return
+
+        val sourcePath = Path.of(source)
+        destinations.forEachIndexed { index, destination ->
+            val destinationPath = Path.of(destination)
+            destinationPath.parent?.let { Files.createDirectories(it) }
+            Files.copy(sourcePath, destinationPath, StandardCopyOption.REPLACE_EXISTING)
+            put(context, "$outputKey.copy.$index", destinationPath.toString())
+        }
+        put(context, "$outputKey.copies", destinations.joinToString(","))
+    }
+
     private val BigDataService.key: String
         get() = name.lowercase().replace('_', '-')
 }

extensions/src/test/kotlin/org/openprojectx/bigdata/test/extensions/kerberos/KerberosMaterialExtensionTest.kt

@@ -0,0 +1,36 @@
+package org.openprojectx.bigdata.test.extensions.kerberos
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+import org.openprojectx.bigdata.test.extensions.config.BigDataExtensionsConfigLoader
+
+class KerberosMaterialExtensionTest {
+    @Test
+    fun `loads local kerberos material copy paths from toml`() {
+        val extension = BigDataExtensionsConfigLoader().load(
+            """
+            [kerberosMaterial]
+            enabled = true
+            id = "kerberos-copy"
+            localClientKeytabCopyPaths = [
+              "build/app/client.keytab",
+              "build/worker/client.keytab"
+            ]
+            localKrb5ConfCopyPaths = [
+              "build/app/krb5.conf",
+              "build/worker/krb5.conf"
+            ]
+            """.trimIndent(),
+        ).single() as KerberosMaterialExtension
+
+        assertEquals("kerberos-copy", extension.id)
+        assertEquals(
+            listOf("build/app/client.keytab", "build/worker/client.keytab"),
+            extension.localClientKeytabCopyPaths,
+        )
+        assertEquals(
+            listOf("build/app/krb5.conf", "build/worker/krb5.conf"),
+            extension.localKrb5ConfCopyPaths,
+        )
+    }
+}