models: remove belongs_to_creator macro.

The belongs_to_creator macro was used to initialize the creator_id field
to the CurrentUser. This made tests complicated because it meant you had
to create and set the current user every time you wanted to create an
object, when lead to the current user being set over and over again. It
also meant you had to constantly be aware of what the CurrentUser was in
many different contexts, which was often confusing. Setting creators
explicitly simplifies everything greatly.

test/unit/user_feedback_test.rb

@@ -2,37 +2,25 @@ require 'test_helper'
 
 class UserFeedbackTest < ActiveSupport::TestCase
   context "A user's feedback" do
-    setup do
-      CurrentUser.ip_addr = "127.0.0.1"
-    end
-
-    teardown do
-      CurrentUser.user = nil
-      CurrentUser.ip_addr = nil
-    end
-
     should "create a dmail" do
       user = FactoryBot.create(:user)
       gold = FactoryBot.create(:gold_user)
       member = FactoryBot.create(:user)
-
       dmail = <<~EOS.chomp
         @#{gold.name} created a "positive record":/user_feedbacks?search[user_id]=#{user.id} for your account:
 
         good job!
       EOS
 
-      CurrentUser.user = gold
       assert_difference("Dmail.count", 1) do
-        FactoryBot.create(:user_feedback, :user => user, :body => "good job!")
+        create(:user_feedback, creator: gold, user: user, body: "good job!")
         assert_equal(dmail, user.dmails.last.body)
       end
     end
 
     should "not validate if the creator is the user" do
-      gold_user = FactoryBot.create(:gold_user)
-      CurrentUser.user = gold_user
-      feedback = FactoryBot.build(:user_feedback, :user => gold_user)
+      user = FactoryBot.create(:gold_user)
+      feedback = build(:user_feedback, creator: user, user: user)
       feedback.save
       assert_equal(["You cannot submit feedback for yourself"], feedback.errors.full_messages)
     end
@@ -42,12 +30,10 @@ class UserFeedbackTest < ActiveSupport::TestCase
       gold = FactoryBot.create(:gold_user)
       member = FactoryBot.create(:user)
 
-      CurrentUser.user = gold
-      feedback = FactoryBot.create(:user_feedback, :user => user)
+      feedback = FactoryBot.create(:user_feedback, creator: gold, user: user)
       assert(feedback.errors.empty?)
 
-      CurrentUser.user = member
-      feedback = FactoryBot.build(:user_feedback, :user => user)
+      feedback = build(:user_feedback, creator: member, user: user)
       feedback.save
       assert_equal(["You must be gold"], feedback.errors.full_messages)
     end