Dont match mention in url query string (#25656)

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

.rubocop_todo.yml

@@ -255,10 +255,6 @@ RSpec/MultipleMemoizedHelpers:
 RSpec/NestedGroups:
   Max: 6
 
-RSpec/PendingWithoutReason:
-  Exclude:
-    - 'spec/models/account_spec.rb'
-
 # This cop supports unsafe autocorrection (--autocorrect-all).
 Rails/ApplicationController:
   Exclude:

app/models/account.rb

@@ -66,7 +66,7 @@ class Account < ApplicationRecord
   BACKGROUND_REFRESH_INTERVAL = 1.week.freeze
 
   USERNAME_RE   = /[a-z0-9_]+([a-z0-9_.-]+[a-z0-9_]+)?/i
-  MENTION_RE    = %r{(?<=^|[^/[:word:]])@((#{USERNAME_RE})(?:@[[:word:].-]+[[:word:]]+)?)}i
+  MENTION_RE    = %r{(?<![=/[:word:]])@((#{USERNAME_RE})(?:@[[:word:].-]+[[:word:]]+)?)}i
   URL_PREFIX_RE = %r{\Ahttp(s?)://[^/]+}
   USERNAME_ONLY_RE = /\A#{USERNAME_RE}\z/i
 

spec/models/account_spec.rb

@@ -700,7 +700,7 @@ RSpec.describe Account do
       expect(subject.match('Check this out https://medium.com/@alice/some-article#.abcdef123')).to be_nil
     end
 
-    xit 'does not match URL query string' do
+    it 'does not match URL query string' do
       expect(subject.match('https://example.com/?x=@alice')).to be_nil
     end
   end