Use final modifiers for package-private classes

Author: damianmalczewski

problem4j-spring-web/src/main/java/io/github/problem4j/spring/web/IdentityProblemFormat.java

@@ -18,8 +18,7 @@
 
 import org.jspecify.annotations.Nullable;
 
-/** No-op {@link ProblemFormat} that returns input data unchanged. */
-class IdentityProblemFormat implements ProblemFormat {
+final class IdentityProblemFormat implements ProblemFormat {
 
   static final IdentityProblemFormat INSTANCE = new IdentityProblemFormat();
 

problem4j-spring-web/src/main/java/io/github/problem4j/spring/web/IdentityProblemPostProcessor.java

@@ -20,8 +20,7 @@
 import io.github.problem4j.core.ProblemContext;
 import org.jspecify.annotations.Nullable;
 
-/** No-op {@link ProblemPostProcessor} that returns the {@link Problem} unchanged. */
-class IdentityProblemPostProcessor implements ProblemPostProcessor {
+final class IdentityProblemPostProcessor implements ProblemPostProcessor {
 
   static final IdentityProblemPostProcessor INSTANCE = new IdentityProblemPostProcessor();
 

problem4j-spring-web/src/test/java/io/github/problem4j/spring/web/parameter/ViolationTest.java

@@ -87,7 +87,7 @@ void givenNullFields_whenHashCode_thenDoesNotThrow() {
   void givenViolation_whenToString_thenContainsFieldAndError() {
     Violation violation = new Violation("age", "must be positive");
 
-    assertThat(violation.toString()).contains("age").contains("must be positive");
+    assertThat(violation.toString()).isEqualTo("Violation[field=age, error=must be positive]");
   }
 
   @Test