Fix: Enforce compiler warnings in oauth2-core

To prevent future compiler warnings from being introduced, this change
applies the `compile-warnings-error` plugin to the
`spring-security-oauth2-core` module.

This ensures that any new warnings will fail the build, maintaining
code quality and preventing warning accumulation.

Fixes: gh-18434
Signed-off-by: Pavel Vassiliev <paulvas@gmail.com>
Signed-off-by: paulvas <paulvas@gmail.com>

Author: paulvas

buildSrc/build.gradle

@@ -52,6 +52,10 @@ gradlePlugin {
 			id = "org.springframework.security.check-expected-branch-version"
 			implementationClass = "org.springframework.security.CheckExpectedBranchVersionPlugin"
 		}
+		compileWarningsError {
+			id = "compile-warnings-error"
+			implementationClass = "CompileWarningsErrorPlugin"
+ 		}
 	}
 }
 

buildSrc/src/main/groovy/compile-warnings-error.groovy

@@ -0,0 +1,15 @@
+import org.gradle.api.Plugin
+import org.gradle.api.Project
+import org.gradle.api.tasks.compile.JavaCompile
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
+class CompileWarningsErrorPlugin implements Plugin<Project> {
+    void apply(Project project) {
+        project.tasks.withType(JavaCompile) {
+            options.compilerArgs += "-Werror"
+        }
+        project.tasks.withType(KotlinCompile) {
+            kotlinOptions.allWarningsAsErrors = true
+        }
+    }
+}

oauth2/oauth2-core/spring-security-oauth2-core.gradle

@@ -1,3 +1,7 @@
+plugins {
+	id 'compile-warnings-error'
+}
+
 apply plugin: 'io.spring.convention.spring-module'
 
 dependencies {