get rid of with_deliveries method

It was setting ActionMailer::Base.perform_deliveries for the duration of
the block, but perform_deliveries is a class attribute, so not thread
local and doesn't work as expected in combination with setting
perform_deliveries to true when calling
Setting::MailSettings#reload_mailer_settings! at the start of every
request and every job run

app/mailers/application_mailer.rb

@@ -45,15 +45,6 @@ class ApplicationMailer < ActionMailer::Base
   default from: Proc.new { Setting.mail_from }
 
   class << self
-    # Activates/deactivates email deliveries during +block+
-    def with_deliveries(temporary_state = true, &)
-      old_state = ActionMailer::Base.perform_deliveries
-      ActionMailer::Base.perform_deliveries = temporary_state
-      yield
-    ensure
-      ActionMailer::Base.perform_deliveries = old_state
-    end
-
     def host
       if OpenProject::Configuration.rails_relative_url_root.blank?
         Setting.host_name

app/workers/copy_project_job.rb

@@ -112,20 +112,16 @@ class CopyProjectJob < ApplicationJob
   # rubocop:disable Metrics/AbcSize
   # Most of the cost is from handling errors, we need to check what can be moved around / removed
   def create_project_copy(target_project_params, associations_to_copy, send_mails)
-    errors = []
+    service_result = copy_project(target_project_params, associations_to_copy, send_mails)
+    target_project = service_result.result
+    errors = service_result.errors.full_messages
 
-    ProjectMailer.with_deliveries(send_mails) do
-      service_result = copy_project(target_project_params, associations_to_copy, send_mails)
-      target_project = service_result.result
-      errors = service_result.errors.full_messages
-
-      # We assume the copying worked "successfully" if the project was saved
-      if target_project&.persisted?
-        return target_project, errors
-      else
-        logger.error("Copying project fails with validation errors: #{errors.join("\n")}")
-        return nil, errors
-      end
+    # We assume the copying worked "successfully" if the project was saved
+    if target_project&.persisted?
+      [target_project, errors]
+    else
+      logger.error("Copying project fails with validation errors: #{errors.join("\n")}")
+      [nil, errors]
     end
   rescue ActiveRecord::RecordNotFound => e
     logger.error("Entity missing: #{e.message} #{e.backtrace.join("\n")}")

spec/mailers/user_mailer_spec.rb

@@ -69,40 +69,6 @@ RSpec.describe UserMailer do
     allow(Setting).to receive(:default_language).and_return("en")
   end
 
-  describe "#with_deliveries" do
-    context "with false" do
-      before do
-        described_class.with_deliveries(false) do
-          described_class.test_mail(recipient).deliver_now
-        end
-      end
-
-      it_behaves_like "mail is not sent"
-    end
-
-    context "with true" do
-      before do
-        described_class.with_deliveries(true) do
-          described_class.test_mail(recipient).deliver_now
-        end
-      end
-
-      it_behaves_like "mail is sent"
-    end
-
-    context "with true but user is locked" do
-      let(:recipient) { build_stubbed(:user, status: Principal.statuses[:locked]) }
-
-      before do
-        described_class.with_deliveries(true) do
-          described_class.test_mail(recipient).deliver_now
-        end
-      end
-
-      it_behaves_like "mail is not sent"
-    end
-  end
-
   describe "#test_mail" do
     let(:test_email) { "bob.bobbi@example.com" }
     let(:recipient) { build_stubbed(:user, firstname: "Bob", lastname: "Bobbi", mail: test_email) }