[GH-5915] Clicking on @mention of a user in a post shows the profile popover (#6129)

* post message at-mention profile pop-over

* remove hover effect to special mentions

* make non-clickable the non-existing at-mention username

* fix "video call" position

* use usernameMap instead of initially defined liteUsernameMap

* update per comments

webapp/tests/utils/formatting_at_mentions.test.jsx

@@ -50,21 +50,6 @@ describe('TextFormatting.AtMentions', function() {
         );
     });
 
-    it('Implied at mentions', function() {
-        // PLT-4454 Assume users exist for things that look like at mentions until we support the new mention syntax
-        assert.equal(
-            TextFormatting.autolinkAtMentions('@user', new Map(), {}),
-            '$MM_ATMENTION0',
-            'should imply user exists and replace mention with token'
-        );
-
-        assert.equal(
-            TextFormatting.autolinkAtMentions('@user.', new Map(), {}),
-            '$MM_ATMENTION0.',
-            'should assume username doesn\'t end in punctuation'
-        );
-    });
-
     it('Not at mentions', function() {
         assert.equal(
             TextFormatting.autolinkAtMentions('user@host', new Map(), {user: {}, host: {}}),
@@ -75,5 +60,28 @@ describe('TextFormatting.AtMentions', function() {
             TextFormatting.autolinkAtMentions('user@email.com', new Map(), {user: {}, email: {}}),
             'user@email.com'
         );
+
+        assert.equal(
+            TextFormatting.autolinkAtMentions('@user', new Map(), {}),
+            '@user'
+        );
+
+        assert.equal(
+            TextFormatting.autolinkAtMentions('@user.', new Map(), {}),
+            '@user.',
+            'should assume username doesn\'t end in punctuation'
+        );
+
+        assert.equal(
+            TextFormatting.autolinkAtMentions('@will', new Map(), {william: {}}),
+            '@will',
+            'should return same text without token'
+        );
+
+        assert.equal(
+            TextFormatting.autolinkAtMentions('@william', new Map(), {will: {}}),
+            '@william',
+            'should return same text without token'
+        );
     });
 });

webapp/tests/utils/formatting_hashtags.test.jsx

@@ -166,7 +166,7 @@ describe('TextFormatting.Hashtags', function() {
         };
         assert.equal(
             TextFormatting.formatText('#@test', options).trim(),
-            "<p>#<a class='mention-link' href='#' data-mention='test'>@test</a></p>"
+            "<p>#<span data-mention='test'><a class='mention-link' href='#'>@test</a></span></p>"
         );
 
         assert.equal(