Attach meta data for transactional email for bounce processing
Created by: Kajakaran
issue linked to https://github.com/cividesk/com.cividesk.email.sparkpost/issues/6
- Create mailing which is intended to handle transactional email
- Create mailing job attaching above mailing
- Above both done in install hook
- In 'alterMailParams' hook, create metadata and attach to params[returnPath]
- Use above data to our unique civi bounce process key - 'X-CiviMail-Bounce'