Refactor Participableseparate-banzai-references

There are several changes to this module:

1. The use of an explicit stack in Participable#participants
2. Proc behaviour has been changed
3. Batch permissions checking

== Explicit Stack

Participable#participants no longer uses recursion to process "self" and
all child objects, instead it uses an Array and processes objects in
breadth-first order. This allows us to for example create a single
Gitlab::ReferenceExtractor instance and pass this to any Procs. Re-using
a ReferenceExtractor removes the need for running potentially many SQL
queries every time a Proc is called on a new object.

== Proc Behaviour Changed

Previously a Proc in Participable was expected to return an Array of
User instances. This has been changed and instead it's now expected that
a Proc modifies the Gitlab::ReferenceExtractor passed to it. The return
value of the Proc is ignored.

== Permissions Checking

The method Participable#participants uses
Ability.users_that_can_read_project to check if the returned users have
access to the project of "self" _without_ running multiple SQL queries
for every user.

1 files changed, 23 insertions, 2 deletions

diff --git a/spec/models/note_spec.rb b/spec/models/note_spec.rb
index 5d916f0e6a6..d158de6b967 100644
--- a/spec/models/note_spec.rb
+++ b/spec/models/note_spec.rb
@@ -93,8 +93,19 @@ describe Note, models: true do
     let!(:note2) { create(:note) }
 
     it "reads the rendered note body from the cache" do
-      expect(Banzai::Renderer).to receive(:render).with(note1.note, pipeline: :note, cache_key: [note1, "note"], project: note1.project)
-      expect(Banzai::Renderer).to receive(:render).with(note2.note, pipeline: :note, cache_key: [note2, "note"], project: note2.project)
+      expect(Banzai::Renderer).to receive(:render).
+        with(note1.note,
+             pipeline: :note,
+             cache_key: [note1, "note"],
+             project: note1.project,
+             author: note1.author)
+
+      expect(Banzai::Renderer).to receive(:render).
+        with(note2.note,
+             pipeline: :note,
+             cache_key: [note2, "note"],
+             project: note2.project,
+             author: note2.author)
 
       note1.all_references
       note2.all_references
@@ -195,4 +206,14 @@ describe Note, models: true do
       expect { note.valid? }.to change(note, :line_code).to(nil)
     end
   end
+
+  describe '#participants' do
+    it 'includes the note author' do
+      project = create(:project, :public)
+      issue = create(:issue, project: project)
+      note = create(:note_on_issue, noteable: issue, project: project)
+
+      expect(note.participants).to include(note.author)
+    end
+  end
 end