Merge pull request #934 from theodi/feature-certificate-campaigns

Improve reliability of certificate import
Show request to claim certificate when not the owner.
Email should definitely be sent async

Otherwise timeouts on the smtp server can bubble up to the user.
Save record to database and use id as parameter for queue

This is less data to serialize and there is now a record of who took the transfer.
Put the owner changing responsibility on the dataset model
Use active support method for non-nil check
In development log email to stdout from jobs worker
Test the actual exploit the code is trying to protect from
Create claim model
Add certificate claim model

I didn’t do this as an extension of transfer as the switching of
logic would’ve lost clarity and there is no reason to limit claims to
a one to one relationship like there is with owner initiated transfers