feat: new background work process

This removes all previous dependencies on RabbitMQ and the need to run separate cron and requeueing processes.

config/cron.rb

@@ -1,30 +0,0 @@
-# frozen_string_literal: true
-
-module Clockwork
-
-  configure do |config|
-    config[:tz] = "UTC"
-    config[:logger] = Postal.logger
-  end
-
-  every 1.minute, "every-1-minutes" do
-    RequeueWebhooksJob.queue(:main)
-    SendNotificationsJob.queue(:main)
-  end
-
-  every 1.hour, "every-hour", at: ["**:15"] do
-    CheckAllDNSJob.queue(:main)
-    ExpireHeldMessagesJob.queue(:main)
-    CleanupAuthieSessionsJob.queue(:main)
-  end
-
-  every 1.hour, "every-hour", at: ["**:45"] do
-    PruneWebhookRequestsJob.queue(:main)
-  end
-
-  every 1.day, "every-day", at: ["03:00"] do
-    ProcessMessageRetentionJob.queue(:main)
-    PruneSuppressionListsJob.queue(:main)
-  end
-
-end

config/initializers/logging.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 begin
   def add_exception_to_payload(payload, event)
     return unless exception = event.payload[:exception_object]

config/postal.defaults.yml

@@ -40,16 +40,6 @@ message_db:
   password: <%= ENV.fetch('MESSAGE_DB_PASSWORD', '') %>
   prefix: <%= ENV.fetch('MESSAGE_DB_PREFIX', 'postal') %>
 
-rabbitmq:
-  host: <%= ENV.fetch('RABBITMQ_HOST', '127.0.0.1') %>
-  port: <%= ENV.fetch('RABBITMQ_PORT', '5672') %>
-  username: <%= ENV.fetch('RABBITMQ_USERNAME', 'postal') %>
-  password: <%= ENV.fetch('RABBITMQ_PASSWORD', '') %>
-  vhost: <%= ENV.fetch('RABBITMQ_VHOST', '/postal') %>
-  tls: <%= ENV.fetch('RABBITMQ_TLS', 'false') %>
-  verify_peer: <%= ENV.fetch('RABBITMQ_VERIFY_PEER', 'true') %>
-  tls_ca_certificates: <%= ENV.fetch('RABBITMQ_TLS_CA_CERTIFICATES', '/etc/ssl/certs/ca-certificates.crt'.split(',').inspect) %>
-
 logging:
   rails_log: <%= ENV.fetch('LOGGING_RAILS_LOG', 'false') %>
   graylog:
@@ -57,9 +47,6 @@ logging:
     port: <%= ENV.fetch('GRAYLOG_PORT', '12201') %>
     facility: <%= ENV.fetch('GRAYLOG_FACILITY', 'postal') %>
 
-workers:
-  threads: <%= ENV.fetch('WORKER_THREADS', '4') %>
-
 smtp_server:
   port: <%= ENV.fetch('SMTP_SERVER_PORT', '25') %>
   bind_address: "<%= ENV.fetch('SMTP_SERVER_BIND_ADDRESS', '::') %>"