several bug fixes around entity API
several bug fixes around entity API

Foreign key ACL binding enforcement for POST /entity/ requests were
bypassed if the foreign key was covered by a uniqueness constraint in
the referring table. This was a legacy of how the original enforcement
was refactored between insert, update, and upsert request paths.

Raise a Conflict error rather than internal server error for PUT
/entity/ (upsert) if there are no client-managed key columns available
to correlate input to existing stored rows.

Fix a typo leading to internal server errors during one foreign key
ACL binding enforcement path.

informatics-isi-edu/ermrest,informatics-isi-edu/ermrest