Dont match mention in url query string (mastodon#25656)

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

app/models/account.rb

@@ -64,9 +64,9 @@ class Account < ApplicationRecord
     trust_level
   )
 
-  USERNAME_RE   = /[a-z0-9_]+([a-z0-9_\.-]+[a-z0-9_]+)?/i
-  MENTION_RE    = /(?<=^|[^\/[:word:]])@((#{USERNAME_RE})(?:@[[:word:]\.\-]+[[:word:]]+)?)/i
-  URL_PREFIX_RE = /\Ahttp(s?):\/\/[^\/]+/
+  USERNAME_RE   = /[a-z0-9_]+([a-z0-9_.-]+[a-z0-9_]+)?/i
+  MENTION_RE    = %r{(?<![=/[:word:]])@((#{USERNAME_RE})(?:@[[:word:].-]+[[:word:]]+)?)}i
+  URL_PREFIX_RE = %r{\Ahttp(s?)://[^/]+}
   USERNAME_ONLY_RE = /\A#{USERNAME_RE}\z/i
 
   include Attachmentable

spec/models/account_spec.rb

@@ -695,7 +695,7 @@
       expect(subject.match('Check this out https://medium.com/@alice/some-article#.abcdef123')).to be_nil
     end
 
-    xit 'does not match URL querystring' do
+    it 'does not match URL query string' do
       expect(subject.match('https://example.com/?x=@alice')).to be_nil
     end
   end