autocomplete: Exclude user from autocomplete popup if deactivated

Deactivated users can not be mentioned, so this commit ensures that
deactivated users are excluded from the list that gets rendered in
autocomplete popup.

Fixes: #451

Author: Khader-1

lib/model/autocomplete.dart

@@ -288,6 +288,8 @@ class MentionAutocompleteQuery {
   bool testUser(User user, AutocompleteDataCache cache) {
     // TODO(#236) test email too, not just name
 
+    if (!user.isActive) return false;
+
     return _testName(user, cache);
   }
 

test/model/autocomplete_test.dart

@@ -312,6 +312,12 @@ void main() {
       expected ? check(result).isTrue() : check(result).isFalse();
     }
 
+    test('user is always excluded when not active regardless of other criteria', () {
+      doCheck('Full Name', eg.user(fullName: 'Full Name', isActive: false), false);
+      // When active then other criteria will be checked
+      doCheck('Full Name', eg.user(fullName: 'Full Name', isActive: true), true);
+    });
+
     test('user is included if fullname words match the query', () {
       doCheck('', eg.user(fullName: 'Full Name'), true);
       doCheck('', eg.user(fullName: ''), true); // Unlikely case, but should not crash