feat: Add custom UnauthorizedException + mapper

Resolves #52 (closed)

This MR adds a custom UnauthorizedException as well as a corresponding mapper class. This approach was used over the javax.rs.NotAuthorizedException since it exhibited odd behavior when paired with a mapper.

Logging the javax.rs.NotAuthorizedException within the ExceptionMapper would not reveal the cause. This behavior is not desirable since it does not provide adequate information when it is thrown in response to a separate exception bubbling up.

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

+/*********************************************************************
+* Copyright (c) 2023 Eclipse Foundation.
+*
+* This program and the accompanying materials are made
+* available under the terms of the Eclipse Public License 2.0
+* which is available at https://www.eclipse.org/legal/epl-2.0/
+*
+* Author: Zachary Sabourin <zachary.sabourin@eclipse-foundation.org>
+*
+* SPDX-License-Identifier: EPL-2.0
+**********************************************************************/
+package org.eclipsefoundation.core.exception;
+
+/**
+ * A Custom exception used to indicate an unauthorized request.
+ * Supports being thrown as a standalone exception as well as a wrapper
+ * for previously bubbled up exceptions.
+ * 
+ * Used in place of javax.rs.NotAuthorizedException as it does not properly
+ * log the cause of the exception when used with an ExceptionMapper.
+ */
+public class UnauthorizedException extends RuntimeException {
+
+    public UnauthorizedException(String message) {
+        super(message);
+    }
+
+    public UnauthorizedException(String message, Throwable cause) {
+        super(message, cause);
+    }
+}