[FIX] mail: mention special char=>link partner

This is a regression from: 10f0766b3. In it the visual side was solved,
but unexpectedly the functional side still worked on unescaped content.

Thus visually a @partnèr could be seen as a link, but it was no anymore
added as follower.

Without change, modified test fails with:

 mentioned partners are sent to server (expected: [1], result: [])

note: change is partial backport of 12.2 e2f20ffa9

opw-1931247
closes #30846

addons/mail/static/src/js/composers/mention_manager.js

@@ -52,10 +52,8 @@ var MentionManager = Widget.extend({
     getListenerSelection: function (delimiter) {
         var listener = _.findWhere(this._listeners, { delimiter: delimiter });
         if (listener) {
-            var inputMentions = this._composer
-                                    .$input
-                                    .val()
-                                    .match(new RegExp(delimiter+'[^ ]+(?= | )', 'g'));
+            var escapedVal = _.escape(this._composer.$input.val());
+            var inputMentions = escapedVal.match(new RegExp(delimiter+'[^ ]+(?= | )', 'g'));
             return this._validateSelection(listener.selection, inputMentions);
         }
         return [];

addons/mail/static/tests/discuss_tests.js

@@ -424,7 +424,7 @@ QUnit.test('@ mention in channel', function (assert) {
 });
 
 QUnit.test('@ mention with special chars', function (assert) {
-    assert.expect(10);
+    assert.expect(11);
     var done = assert.async();
     var fetchListenersDef = $.Deferred();
     var receiveMessageDef = $.Deferred();
@@ -452,6 +452,9 @@ QUnit.test('@ mention with special chars', function (assert) {
                 ]);
             }
             if (args.method === 'message_post') {
+                assert.deepEqual(args.kwargs.partner_ids, [1],
+                    "mentioned partners are sent to server"
+                )
                 var data = {
                     author_id: ["42", "Me"],
                     body: args.kwargs.body,