Add findByManuscriptId and pubdate

Now packages can be queried by manuscript ID and we can set the
publishOn date. temporary metadata field used here
Handler for updating data package with pub date
Instantiate release date handler in handler group
Add dc.date.blackoutUntil to metadata registry
Incorporate dc.date.blackoutUntil
Remove unused imports
Support for approving/rejecting based on DOI
Prefer data package DOI when approving/rejecting
Add tests for AuthorizationTuple
Cleanup dangling TODOs
Improve response generation

Includes ErrorResponse for informing about errors
REST actions return more information
Refactor to wrap errors in an errors: object

Also removed unpopulated fields
Include absolute paths in error
Notes for ManuscriptReleaseDateHandler
Provider to format/indent JSON responses