Show OAuth errors

oauth/index.html

@@ -12,6 +12,7 @@
 	<style>
 		* { font-family: Arial, Helvetica, sans-serif; }
 		body { padding-left: 10px; padding-right: 10px; }
+		.error { color: red; font-weight: bold; }
 		.button-large { width: 120px; height: 30px; font-weight: bold; }
 	</style>
 	<script>
@@ -20,6 +21,17 @@
 		function load() {
 			document.getElementById('oauth').addEventListener('click', oauth);
 			document.getElementById('year').textContent= new Date().getFullYear();
+
+			try {
+				var url = new URL(window.location.href);
+				var error = url.searchParams.get('error');
+				if (error) {
+					document.getElementById('error').innerText = error;
+					document.getElementById('error').style.display = 'block';
+				}
+			} catch (error) {
+				console.error(error);
+			}
 		}
 
 		function oauth() {
@@ -31,6 +43,7 @@
 	<h1>FairEmail</h1>
 	<p><img src="https://raw.githubusercontent.com/M66B/FairEmail/master/app/src/main/ic_launcher-web.png" alt="FairEmail" height="72" width="72" /></p>
 	<h2>&#x1F6E1; OAuth</h2>
+	<p id="error" class="error" style="display: none;"></p>
 	<p><button id="oauth" class="button-large">Continue</button> to the app</p>
 	<noscript><h2>Please enable JavaScript or disable your ad blocker</h2></noscript>
 	<br>