Implement addRequest in UI

- addRequest modal
  - Error box inside addRequest modal
- Generic message modal
- URL validation - same code as server
- Update /api/addRequest to get requester from session
- Fix return of requests.addRequest() for already requested
- Make requests.addRequest() return 201 when created

views/main.eta

@@ -30,10 +30,15 @@
 			</select>
 			<input type="checkbox" id="allRequests" onchange="updateTable()">View requests in any state</input>
 		</div>
-		<div id="addRequestModalBackground" onclick="closeAddRequestModal()">
-			<div id="addRequestModal">
-				<div id="addRequestModalClose"><a href="#" onclick="closeAddRequestModal()">&times;</a></div>
+		<div id="modalBackground">
+			<div class="modal" id="messageModal">
+				<div class="modalClose"><a href="#" onclick="closeMessageModal()">&times;</a></div>
+				<span id="messageModalText"></span>
+			</div>
+			<div class="modal" id="addRequestModal">
+				<div class="modalClose"><a href="#" onclick="closeAddRequestModal()">&times;</a></div>
 				<h1>Add Request</h1>
+				<div class="error" id="addRequestError"></div>
 				<span id="addRequestInputContainer">
 					URL: <input id="addRequestUrl" placeholder="https://www.youtube.com/watch?v=dQw4w9WgXcQ"></input>
 					<button onclick="validateAndSubmitRequest()">Request</button><br>
@@ -43,4 +48,3 @@
 		</div>
 	</body>
 </html>
-