Use existing config access to local_domain value (#30509)

spec/requests/well_known/oauth_metadata_spec.rb

@@ -6,7 +6,7 @@ describe 'The /.well-known/oauth-authorization-server request' do
   let(:protocol) { ENV.fetch('LOCAL_HTTPS', true) ? :https : :http }
 
   before do
-    host! ENV.fetch('LOCAL_DOMAIN')
+    host! Rails.configuration.x.local_domain
   end
 
   it 'returns http success with valid JSON response' do

spec/support/signed_request_helpers.rb

@@ -6,7 +6,7 @@ module SignedRequestHelpers
 
     headers ||= {}
     headers['Date'] = Time.now.utc.httpdate
-    headers['Host'] = ENV.fetch('LOCAL_DOMAIN')
+    headers['Host'] = Rails.configuration.x.local_domain
     signed_headers = headers.merge('(request-target)' => "get #{path}").slice('(request-target)', 'Host', 'Date')
 
     key_id = ActivityPub::TagManager.instance.key_uri_for(sign_with)

spec/system/profile_spec.rb

@@ -7,7 +7,7 @@ describe 'Profile' do
 
   subject { page }
 
-  let(:local_domain) { ENV['LOCAL_DOMAIN'] }
+  let(:local_domain) { Rails.configuration.x.local_domain }
 
   before do
     as_a_logged_in_user