fix: Fix exception mapper naming scheme + add 400 mapper

Resolves #44 (closed)

core/src/main/java/org/eclipsefoundation/core/exception/FinalForbiddenException.java

@@ -17,9 +17,9 @@ package org.eclipsefoundation.core.exception;
  *
  * @author Martin Lowe
  */
-public class FinalUnauthorizedException extends RuntimeException {
+public class FinalForbiddenException extends RuntimeException {
 
-  public FinalUnauthorizedException(String message) {
+  public FinalForbiddenException(String message) {
     super(message);
   }