Make sure that the entire Spring AI compiles with Spring 7

* Add GitHub Worklfow that runs the suite with Spring 7
* Uncomment `@Override` from methods implementing from ResponseHandler
* Add custom ApiClient.mustache, original copied from https://github.com/swagger-api/swagger-codegen/blob/92fcc8196bd90fef199c2932903135e3b519f689/modules/swagger-codegen/src/main/resources/Java/ApiClient.mustache and adjusted the use of the HttpHeaders to be compliant with Spring 7
* Adjust ChatCLientExtensions.kt to be compatible with Kotlin 2

Author: filiphr

.github/workflows/pr-check.yml

@@ -24,3 +24,22 @@ jobs:
       - name: Run tests
         run: |
           ./mvnw --batch-mode test
+  spring_7:
+    name: Compile with Spring 7
+    runs-on: ubuntu-latest
+    if: ${{ github.repository_owner == 'spring-projects' }}
+    steps:
+      - name: Checkout source code
+        uses: actions/checkout@v4
+
+      - name: Set up JDK 17
+        uses: actions/setup-java@v4
+        with:
+          java-version: '17'
+          distribution: 'temurin'
+          cache: 'maven'
+
+      - name: Run tests
+        run: |
+          ./mvnw --batch-mode -Dspring-framework.version=7.0.0-RC2 -Dkotlin.version=2.2.0 compile
+    

auto-configurations/common/spring-ai-autoconfigure-retry/src/main/java/org/springframework/ai/retry/autoconfigure/SpringAiRetryAutoConfiguration.java

@@ -86,7 +86,9 @@ public boolean hasError(@NonNull ClientHttpResponse response) throws IOException
 				return response.getStatusCode().isError();
 			}
 
-			@Override
+			// On purposes commented out so that the code can compile both with Spring 6 and Spring 7
+			// @Override
+			@SuppressWarnings("removal")
 			public void handleError(@NonNull ClientHttpResponse response) throws IOException {
 				if (!response.getStatusCode().isError()) {
 					return;