DEV: Automatically require 'rails_helper' in all specs (#16077)

It's very easy to forget to add `require 'rails_helper'` at the top of every core/plugin spec file, and omissions can cause some very confusing/sporadic errors.

By setting this flag in `.rspec`, we can remove the need for `require 'rails_helper'` entirely.

plugins/discourse-narrative-bot/spec/discourse_narrative_bot/advanced_user_narrative_spec.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require 'rails_helper'
-
 RSpec.describe DiscourseNarrativeBot::AdvancedUserNarrative do
   fab!(:narrative_bot) { ::DiscourseNarrativeBot::Base.new }
   fab!(:discobot_user) { narrative_bot.discobot_user }

plugins/discourse-narrative-bot/spec/discourse_narrative_bot/new_user_narrative_spec.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require 'rails_helper'
-
 describe DiscourseNarrativeBot::NewUserNarrative do
   fab!(:welcome_topic) { Fabricate(:topic, title: 'Welcome to Discourse') }
   fab!(:narrative_bot) { ::DiscourseNarrativeBot::Base.new }

plugins/discourse-narrative-bot/spec/discourse_narrative_bot/store_spec.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require 'rails_helper'
-
 describe DiscourseNarrativeBot::Store do
   describe '.set' do
     it 'should set the right value in the plugin store' do

plugins/discourse-narrative-bot/spec/discourse_narrative_bot/track_selector_spec.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require 'rails_helper'
-
 describe DiscourseNarrativeBot::TrackSelector do
   let(:user) { Fabricate(:user) }
   let(:narrative_bot) { ::DiscourseNarrativeBot::Base.new }

plugins/discourse-narrative-bot/spec/jobs/onceoff/grant_badges_spec.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require 'rails_helper'
-
 RSpec.describe Jobs::DiscourseNarrativeBot::GrantBadges do
   let(:user) { Fabricate(:user) }
   let(:other_user) { Fabricate(:user) }

plugins/discourse-narrative-bot/spec/jobs/onceoff/remap_old_bot_images_spec.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require 'rails_helper'
-
 describe Jobs::DiscourseNarrativeBot::RemapOldBotImages do
   context "when bot's post contains an old link" do
     let!(:post) do

plugins/discourse-narrative-bot/spec/jobs/send_default_welcome_message_spec.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require 'rails_helper'
-
 RSpec.describe Jobs::SendDefaultWelcomeMessage do
   let(:user) { Fabricate(:user) }
 

plugins/discourse-narrative-bot/spec/lib/certificate_generator_spec.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require 'rails_helper'
-
 RSpec.describe DiscourseNarrativeBot::CertificateGenerator do
   let(:user) { Fabricate(:user) }
   let(:avatar_url) { 'http://test.localhost/cdn/avatar.png' }

plugins/discourse-narrative-bot/spec/requests/discobot_certificate_spec.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require 'rails_helper'
-
 describe "Discobot Certificate" do
   let(:user) { Fabricate(:user, name: 'Jeff Atwood') }
 

plugins/discourse-narrative-bot/spec/requests/discobot_welcome_post_spec.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require 'rails_helper'
-
 describe "Discobot welcome post" do
   let(:user) { Fabricate(:user) }
 

plugins/discourse-narrative-bot/spec/user_spec.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require 'rails_helper'
-
 describe User do
   let(:user) { Fabricate(:user) }
   let(:profile_page_url) { "#{Discourse.base_url}/users/#{user.username}" }