Refactor AutocompleteController

This refactors the AutocompleteController according to the guidelines
and boundaries discussed in
https://gitlab.com/gitlab-org/gitlab-ce/issues/49653. Specifically,
ActiveRecord logic is moved to different finders, which are then used in
the controller. View logic in turn is moved to presenters, instead of
directly using ActiveRecord's "to_json" method.

The finder MoveToProjectFinder is also adjusted according to the
abstraction guidelines and boundaries, resulting in a much more simple
finder.

By using finders (and other abstractions) more actively, we can push a
lot of logic out of the controller. We also remove the need for various
"before_action" hooks, though this could be achieved without using
finders as well.

The various finders related to AutcompleteController have also been
moved into a namespace. This removes the need for calling everything
"AutocompleteSmurfFinder", instead you can use
"Autocomplete::SmurfFinder".

1 files changed, 19 insertions, 0 deletions

diff --git a/app/models/concerns/optionally_search.rb b/app/models/concerns/optionally_search.rb
new file mode 100644
index 00000000000..dec97b7dee8
--- /dev/null
+++ b/app/models/concerns/optionally_search.rb
@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+module OptionallySearch
+  extend ActiveSupport::Concern
+
+  module ClassMethods
+    def search(*)
+      raise(
+        NotImplementedError,
+        'Your model must implement the "search" class method'
+      )
+    end
+
+    # Optionally limits a result set to those matching the given search query.
+    def optionally_search(query = nil)
+      query.present? ? search(query) : all
+    end
+  end
+end