Merge branch 'fix_bug_with_mime_types' into 'master'

Fix validation method regarding MIME type keys

See merge request gitlab-org/gitlab!65954

app/models/user.rb

@@ -2106,7 +2106,7 @@ class User < ApplicationRecord
   end
 
   def check_username_format
-    return if username.blank? || Mime::EXTENSION_LOOKUP.keys.none? { |type| username.end_with?(type) }
+    return if username.blank? || Mime::EXTENSION_LOOKUP.keys.none? { |type| username.end_with?(".#{type}") }
 
     errors.add(:username, _('ending with MIME type format is not allowed.'))
   end

spec/models/user_spec.rb

@@ -394,6 +394,7 @@ RSpec.describe User do
 
           expect(user).not_to be_valid
           expect(user.errors.full_messages).to include('Username ending with MIME type format is not allowed.')
+          expect(build(:user, username: "test#{type}")).to be_valid
         end
       end