ci: 👷 Github actions setup, heroku deployment

Redis cache store, Production Dockerfile, Github actions workflow

config/environments/production.rb

@@ -58,8 +58,7 @@ Rails.application.configure do
   # Prepend all log lines with the following tags.
   config.log_tags = [:request_id]
 
-  # Use a different cache store in production.
-  # config.cache_store = :mem_cache_store
+  config.cache_store = :redis_cache_store, { url: ENV['REDIS_URL'] }
 
   # Use a real queuing backend for Active Job (and separate queues per environment)
   # config.active_job.queue_adapter     = :resque
@@ -94,5 +93,5 @@ Rails.application.configure do
   # Do not dump schema after migrations.
   config.active_record.dump_schema_after_migration = false
 
-  Rails.application.routes.default_url_options[:host] = "#{ENV['HOSTNAME']}:#{ENV['RAILS_PORT']}"
+  Rails.application.routes.default_url_options[:host] = ENV['HOSTNAME']
 end