Draft: WS-4174 Custom email cleanup

Daniel Nemergutrequested to merge
ws4174-custom_email_cleanup into development

This is in a draft state until development is caught up with the 2.9.0 rc branch.

Some cleanup that I did when fixing WS-4174. This makes a notification endpoint to retrieve a single notification template rather than iterating through all of them for the correct one. There are also some swagger doc fixes here.

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