build curator workflow for contacting authors

[cpritcha]

This is an omnibus issue for the author contact curator workflow.

Add a curator workflow that enables a curator to contact authors of valid publications with missing or invalid code archive urls:

Tasks:

• [ ] first cut #147
• [ ] implement and test #71
• [ ] select a set of publications, construct an email based on template(s) to send to the contact authors, reply-to: should be the curator sending the email
• [ ] keep track of emails sent
• [ ] aggregate emails to the same contact author so we don't spam them repeatedly with emails
• [ ] emails include links with unique edit URL to submit a code archive URL back for the given Publications

Some issues / corner cases:

• handle multiple code archive urls, some are valid, some are unreachable/invalid
• allow repeated edits
• edits should submit to a moderation queue, not update-in-place

[alee]

closing, remaining tasks are in #178