Merge branch 'test-improve-gitlab-identifier' into 'master'
Refactor Gitlab::Identifier ## What does this MR do? This refactors `Gitlab::Identifier` so that it: 1. Has tests 2. Caches output in an instance variable to reduce queries 3. Uses only a single query to find a user by an SSH key, instead of 2 ## Why was this MR needed? This code was untested and would execute more SQL queries than needed. See merge request !6680