feat: add dynamic proxy support with Spring Cloud Gateway

- Implement `DynamicProxyGlobalFilter` for routing dynamic proxy requests based on configurable properties.
- Introduce `SpringCloudProxyAutoConfiguration` enabling dynamic proxy functionality.
- Create `DynamicProxyProperties` for centralized configuration (e.g., allowed schemes, path prefix, etc.).
- Add Gradle and project configuration files to set up the project structure, dependencies, and publishing workflows.
- Include Apache License and necessary metadata for open-source distribution.

Author: CoderYellow

.gitignore

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+.gradle
+build/
+!gradle/wrapper/gradle-wrapper.jar
+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### IntelliJ IDEA ###
+.idea/modules.xml
+.idea/jarRepositories.xml
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+.idea/libraries/
+*.iws
+*.iml
+*.ipr
+out/
+!**/src/main/**/out/
+!**/src/test/**/out/
+
+### Kotlin ###
+.kotlin
+
+### Eclipse ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+bin/
+!**/src/main/**/bin/
+!**/src/test/**/bin/
+
+### NetBeans ###
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+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+
+### VS Code ###
+.vscode/
+
+### Mac OS ###
+.DS_Store
+/.idea/

LICENSE

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app/build.gradle.kts

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+plugins {
+    id("buildsrc.convention.kotlin-jvm")
+    id("buildsrc.convention.spring-kotlin")
+}
+
+
+dependencies {
+
+    implementation(project(":spring-cloud-proxy-spring-boot-starter"))
+
+}

app/src/main/kotlin/org/openprojectx/spring/cloud/proxy/app/SpringCloudProxyApplication.kt

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+package org.openprojectx.spring.cloud.proxy.app
+
+import org.springframework.boot.autoconfigure.SpringBootApplication
+import org.springframework.boot.runApplication
+
+
+@SpringBootApplication
+class SpringCloudProxyApplication
+
+fun main(args: Array<String>) {
+
+    runApplication<SpringCloudProxyApplication>(*args)
+}

app/src/main/resources/application.yaml

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+spring:
+  application:
+    name: spring-cloud-proxy

autoconfigure/spring-cloud-proxy-spring-boot-autoconfigure.gradle.kts

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+plugins {
+    id("buildsrc.convention.kotlin-jvm")
+    `kotlin-kapt`
+}
+
+
+dependencies {
+
+    api(project(":core"))
+
+    val bootBom = platform("org.springframework.boot:spring-boot-dependencies:${libs.versions.springBoot.get()}")
+    val cloudBom = platform(libs.springCloudDependencies)
+
+    implementation(bootBom)
+    implementation(cloudBom)
+    kapt(bootBom)
+
+    implementation("org.springframework.boot:spring-boot-autoconfigure")
+    api("org.springframework.boot:spring-boot-starter")
+    kapt("org.springframework.boot:spring-boot-configuration-processor")
+    implementation("org.springframework.cloud:spring-cloud-starter-gateway-server-webflux")
+
+    testImplementation("org.springframework.boot:spring-boot-starter-test")
+    testImplementation("org.springframework.boot:spring-boot-starter-webflux-test")
+    testImplementation("org.testcontainers:testcontainers-junit-jupiter:2.0.3")
+    testImplementation("org.testcontainers:testcontainers:2.0.3")
+    testRuntimeOnly("org.junit.platform:junit-platform-launcher")
+
+
+
+}

autoconfigure/src/main/kotlin/org/openprojectx/spring/cloud/proxy/autoconfigure/DynamicProxyGlobalFilter.kt

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+package org.openprojectx.spring.cloud.proxy.autoconfigure
+
+import org.springframework.cloud.gateway.filter.GatewayFilterChain
+import org.springframework.cloud.gateway.filter.GlobalFilter
+import org.springframework.cloud.gateway.filter.RouteToRequestUrlFilter
+import org.springframework.cloud.gateway.support.ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR
+import org.springframework.core.Ordered
+import org.springframework.http.HttpStatus
+import org.springframework.web.server.ServerWebExchange
+import reactor.core.publisher.Mono
+import java.net.URI
+
+internal class DynamicProxyGlobalFilter(
+    private val properties: DynamicProxyProperties,
+) : GlobalFilter, Ordered {
+
+    override fun filter(exchange: ServerWebExchange, chain: GatewayFilterChain): Mono<Void> {
+        val path = exchange.request.path.pathWithinApplication().value()
+        val prefix = properties.normalizedPrefix()
+        if (path != prefix && !path.startsWith("$prefix/")) return chain.filter(exchange)
+
+        val destination = try {
+            destination(path, exchange.request.uri.rawQuery)
+        } catch (exception: IllegalArgumentException) {
+            return badRequest(exchange, exception.message ?: "Invalid dynamic proxy destination")
+        }
+
+        exchange.attributes[GATEWAY_REQUEST_URL_ATTR] = destination
+        return chain.filter(exchange)
+    }
+
+    private fun destination(path: String, rawQuery: String?): URI {
+        val parts = path.removePrefix(properties.normalizedPrefix()).removePrefix("/").split("/", limit = 4)
+        require(parts.size == 4 && parts[3].isNotEmpty()) {
+            "Expected /{scheme}/{host}/{port}/{target-path}"
+        }
+
+        val (scheme, host, portText, target) = parts
+        require(scheme.lowercase() in properties.allowedSchemes.map(String::lowercase)) {
+            "Unsupported proxy scheme: $scheme"
+        }
+        require(host.isNotBlank()) { "Proxy host must not be blank" }
+        val port = portText.toIntOrNull()
+        require(port != null && port in 1..65535) { "Proxy port must be between 1 and 65535" }
+
+        val authority = URI(scheme.lowercase(), null, host, port, null, null, null).toASCIIString()
+        // target and rawQuery came from the already parsed request URI. Reusing their raw forms avoids
+        // turning an encoded value such as %20 into %2520 on the downstream request.
+        return URI.create(buildString {
+            append(authority).append('/').append(target)
+            if (rawQuery != null) append('?').append(rawQuery)
+        })
+    }
+
+    private fun badRequest(exchange: ServerWebExchange, message: String): Mono<Void> {
+        exchange.response.statusCode = HttpStatus.BAD_REQUEST
+        val body = """{"error":"${message.jsonEscape()}"}""".toByteArray()
+        exchange.response.headers.contentType = org.springframework.http.MediaType.APPLICATION_JSON
+        return exchange.response.writeWith(Mono.just(exchange.response.bufferFactory().wrap(body)))
+    }
+
+    // RouteToRequestUrlFilter first installs the route's placeholder URL; this filter then replaces it.
+    override fun getOrder(): Int = RouteToRequestUrlFilter.ROUTE_TO_URL_FILTER_ORDER + 1
+}
+
+internal fun DynamicProxyProperties.normalizedPrefix(): String =
+    "/" + pathPrefix.trim().trim('/').also { require(it.isNotEmpty()) { "pathPrefix must not be blank" } }
+
+private fun String.jsonEscape(): String = buildString {
+    this@jsonEscape.forEach { character ->
+        when (character) {
+            '\\' -> append("\\\\")
+            '"' -> append("\\\"")
+            '\n' -> append("\\n")
+            '\r' -> append("\\r")
+            '\t' -> append("\\t")
+            else -> append(character)
+        }
+    }
+}