Merge branch 'dz-clarify-constrainer-query' into 'master'

Explain why we use select all for project_url_constrainer.rb

See merge request !13425

lib/constraints/project_url_constrainer.rb

@@ -6,6 +6,8 @@ class ProjectUrlConstrainer
 
     return false unless DynamicPathValidator.valid_project_path?(full_path)
 
+    # We intentionally allow SELECT(*) here so result of this query can be used
+    # as cache for further Project.find_by_full_path calls within request 
     Project.find_by_full_path(full_path, follow_redirects: request.get?).present?
   end
 end