Support for joining New Groups via invite links

ts/util/webSafeBase64.ts

@@ -0,0 +1,25 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+export function toWebSafeBase64(base64: string): string {
+  return base64.replace(/\//g, '_').replace(/\+/g, '-').replace(/=/g, '');
+}
+
+export function fromWebSafeBase64(webSafeBase64: string): string {
+  const base64 = webSafeBase64.replace(/_/g, '/').replace(/-/g, '+');
+
+  // Ensure that the character count is a multiple of four, filling in the extra
+  //   space needed with '='
+  const remainder = base64.length % 4;
+  if (remainder === 3) {
+    return `${base64}=`;
+  }
+  if (remainder === 2) {
+    return `${base64}==`;
+  }
+  if (remainder === 1) {
+    return `${base64}===`;
+  }
+
+  return base64;
+}