[THINK] Follow-up from "Overage acceptance mailer"

The following discussion from !13774 should be addressed:

• @vshumilo started a discussion:

  thought: Yeah it is a bit unfortunate that for us gitlab_credits_plan is actually an id but to find the id we are now querying the Zuora::Local::ProductRatePlan table just to use it to query it again 🤔

  note to self! We should do something about it specially since the "new way" is to work with this object directly 🤔

  Adding the comment to resolve it with an issue so I can track this