feat: migrate configuration format from JSON to TOML

- Replaced JSON configuration with TOML for `BigDataExtensions` across examples, tests, and documentation.
- Updated `BigDataExtensionsConfigLoader` to support parsing TOML files via a custom parser.
- Converted all JSON examples in documentation and tests to TOML for improved clarity and compactness.
- Added new TOML resource file `spark-bigdata-extensions.toml` in Spark example.
- Improved inline array and table handling for declarative test data configurations with TOML.

Author: CoderYellow

README.md

@@ -56,10 +56,10 @@ The built-in extensions currently support:
 - `s3Jceks`: creates an HDFS-backed JCEKS file from the LocalStack S3 endpoint credentials and exposes `s3-jceks.credential-provider.path`.
 - `kafkaAvro`: creates Kafka topics and produces Avro records through Schema Registry from inline JSON records or a records resource.
 
-JUnit usage is declaration-driven. The test declares the services with `@BigDataTest`, then points `@BigDataExtensions` at one or more JSON resources:
+JUnit usage is declaration-driven. The test declares the services with `@BigDataTest`, then points `@BigDataExtensions` at one or more TOML resources:
 
 ```kotlin
-@BigDataExtensions("classpath:bigdata-extensions.json")
+@BigDataExtensions("classpath:bigdata-extensions.toml")
 @BigDataTest(
     hdfs = true,
     kafka = true,
@@ -76,27 +76,22 @@ class MyIntegrationTest {
 
 Example config:
 
-```json
-{
-  "s3Jceks": {
-    "enabled": true,
-    "hdfsDir": "/bigdata-test/spark",
-    "fileName": "s3.jceks"
-  },
-  "kafkaAvro": {
-    "enabled": true,
-    "topics": [
-      {
-        "name": "events",
-        "schema": "classpath:schemas/event.avsc",
-        "records": [
-          {"key": "alpha", "value": {"id": 1, "name": "alpha"}},
-          {"key": "beta", "value": {"id": 2, "name": "beta"}}
-        ]
-      }
-    ]
-  }
-}
+```toml
+[s3Jceks]
+enabled = true
+hdfsDir = "/bigdata-test/spark"
+fileName = "s3.jceks"
+
+[kafkaAvro]
+enabled = true
+
+[[kafkaAvro.topics]]
+name = "events"
+schema = "classpath:schemas/event.avsc"
+records = [
+  { key = "alpha", value = { id = 1, name = "alpha" } },
+  { key = "beta", value = { id = 2, name = "beta" } },
+]
 ```
 
 For future extension modules, implement `BigDataExtension` directly for programmatic use or publish a `BigDataExtensionProvider` via `ServiceLoader`. Providers are selected from config entries under `extensions` by `type`, and extensions can hook lifecycle events such as `AFTER_KIT_START`, `BEFORE_TEST_EXECUTION`, and `AFTER_ALL`.

doc/user-guide.adoc

@@ -307,7 +307,7 @@ Use `@BigDataExtensions` with one or more config resources.
 
 [source,kotlin]
 ----
-@BigDataExtensions("classpath:bigdata-extensions.json")
+@BigDataExtensions("classpath:bigdata-extensions.toml")
 @BigDataTest(
     hdfs = true,
     kafka = true,
@@ -328,17 +328,14 @@ Extension output is exposed through `BigDataExtensionResult`.
 
 The `s3Jceks` extension creates a Hadoop credential provider file in HDFS and stores LocalStack S3 credentials in it.
 
-[source,json]
+[source,toml]
 ----
-{
-  "s3Jceks": {
-    "enabled": true,
-    "hdfsDir": "/bigdata-test/spark",
-    "fileName": "s3.jceks",
-    "accessKeyAlias": "fs.s3a.access.key",
-    "secretKeyAlias": "fs.s3a.secret.key"
-  }
-}
+[s3Jceks]
+enabled = true
+hdfsDir = "/bigdata-test/spark"
+fileName = "s3.jceks"
+accessKeyAlias = "fs.s3a.access.key"
+secretKeyAlias = "fs.s3a.secret.key"
 ----
 
 Outputs:
@@ -352,26 +349,21 @@ Use `s3-jceks.credential-provider.path` as `hadoop.security.credential.provider.
 
 The `kafkaAvro` extension creates topics and produces Avro records using Schema Registry.
 
-[source,json]
-----
-{
-  "kafkaAvro": {
-    "enabled": true,
-    "topics": [
-      {
-        "name": "events",
-        "schema": "classpath:schemas/event.avsc",
-        "records": [
-          {"key": "alpha", "value": {"id": 1, "name": "alpha"}},
-          {"key": "beta", "value": {"id": 2, "name": "beta"}}
-        ]
-      }
-    ]
-  }
-}
+[source,toml]
+----
+[kafkaAvro]
+enabled = true
+
+[[kafkaAvro.topics]]
+name = "events"
+schema = "classpath:schemas/event.avsc"
+records = [
+  { key = "alpha", value = { id = 1, name = "alpha" } },
+  { key = "beta", value = { id = 2, name = "beta" } },
+]
 ----
 
-Records can be supplied inline or from a resource. Use this extension when test data should be declarative and reproducible instead of manually wired in every test.
+Records can be supplied inline as compact TOML arrays or from a resource. Use this extension when test data should be declarative and reproducible instead of manually wired in every test.
 
 === Extension Lifecycle
 

example/spark/src/test/kotlin/org/openprojectx/bigdata/test/example/spark/SparkBigDataTestExample.kt

@@ -18,7 +18,7 @@ import java.nio.charset.StandardCharsets
 import java.nio.file.Files
 import java.time.Duration
 
-@BigDataExtensions("classpath:spark-bigdata-extensions.json")
+@BigDataExtensions("classpath:spark-bigdata-extensions.toml")
 @BigDataTest(
     hdfs = true,
     hiveMetastore = true,

example/spark/src/test/resources/spark-bigdata-extensions.json

@@ -0,0 +1,15 @@
+[s3Jceks]
+enabled = true
+hdfsDir = "/bigdata-test/spark"
+fileName = "s3.jceks"
+
+[kafkaAvro]
+enabled = true
+
+[[kafkaAvro.topics]]
+name = "spark-avro-events"
+schema = "classpath:schemas/spark-event.avsc"
+records = [
+  { key = "alpha", value = { id = 1, name = "alpha" } },
+  { key = "beta", value = { id = 2, name = "beta" } },
+]