feat: Implement P12 certificate generation improvements

- Replace hardcoded P12 password with randomly generated one
- Add p12_password column to certificates table
- Update certificate serializer to include p12 password in response
- Remove deprecated certificate revocation logic
- Add tests for certificate revocation functionality
- Implement async P12 generation via Sidekiq job
- Add job uniqueness to prevent parallel certificate generation

Migration changes:
- Replace p12_password_digest with p12_password column
- Add safety measures for column removal

app/models/concerns/certificate/certificate_concern.rb

@@ -3,17 +3,6 @@ module Certificate::CertificateConcern
   extend ActiveSupport::Concern
 
   class_methods do
-    def tostdout(message)
-      time = Time.zone.now.utc
-      $stdout << "#{time} - #{message}\n" unless Rails.env.test?
-    end
-
-    def update_crl
-      tostdout('Running crlupdater')
-      system('/bin/bash', ENV['crl_updater_path'].to_s)
-      tostdout('Finished running crlupdater')
-    end
-
     def parse_md_from_string(crt)
       return if crt.blank?