Remove private variable usage from models

It seems that `@new_record_before_save` as an instance variable has been
present since around 2007 and it wasn't until Rails 5.1 that things were
changed in such a way to make this inaccessible now.

app/controllers/todos/todo_create_params_helper.rb

@@ -146,9 +146,11 @@ module Todos
     end
 
     def set_id_by_name(group_type, set, name)
-      group = set.where(:name => name).first_or_create
+      group = set.where(:name => name).first_or_initialize
+      group_is_new = group.new_record?
+      group.save if group_is_new
       @attributes["#{group_type}_id"] = group.id
-      return group.new_record_before_save?
+      group_is_new
     end
 
     def set_id_by_id_string(group_type, set, id)

app/models/context.rb

@@ -45,10 +45,6 @@ class Context < ApplicationRecord
     name
   end
 
-  def new_record_before_save?
-    @new_record_before_save
-  end
-
   def no_active_todos?
     return todos.active.count == 0
   end

app/models/project.rb

@@ -118,10 +118,6 @@ class Project < ApplicationRecord
     end
   end
 
-  def new_record_before_save?
-    @new_record_before_save
-  end
-
   def age_in_days
     @age_in_days ||= (Time.current.to_date - created_at.to_date).to_i + 1
   end

test/models/context_test.rb

@@ -61,12 +61,6 @@ class ContextTest < ActiveSupport::TestCase
     assert_equal '', c.name
   end
 
-  def test_new_record_before_save
-    assert !@agenda.new_record_before_save?, "existing records should not be new_record"
-    c = Context.where(:name => "I do not exist").first_or_create
-    assert c.new_record_before_save?, "newly created record should be new_record"
-  end
-
   def test_hide_context
     assert @agenda.active?
     @agenda.hide!

test/models/project_test.rb

@@ -174,12 +174,6 @@ class ProjectTest < ActiveSupport::TestCase
     assert_equal 3, @moremoney.todos.not_completed.count
   end
 
-  def test_new_record_before_save
-    assert !@timemachine.new_record_before_save?, "existing records should not be new_record"
-    p = Project.where(:name => "I do not exist").first_or_create
-    assert p.new_record_before_save?, "newly created record should be new_record"
-  end
-
   def test_shortened_name
     s = "project"*7 # len=49
     p = users(:admin_user).projects.create(:name => s)