Stale read when creating images

Sentry Issue: ARKINDEX-BACKEND-W0

UniqueViolation: duplicate key value violates unique constraint "images_image_server_id_hash_e1ccd087_uniq"
DETAIL:  Key (server_id, hash)=(3, ae4b1f07e16065c81b7681868ba13928) already exists.

  File "django/db/backends/utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)

IntegrityError: duplicate key value violates unique constraint "images_image_server_id_hash_e1ccd087_uniq"
DETAIL:  Key (server_id, hash)=(3, ae4b1f07e16065c81b7681868ba13928) already exists.

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  File "django/db/backends/utils.py", line 66, in execute
    return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
  File "django/db/backends/utils.py", line 75, in _execute_with_wrappers
    return executor(sql, params, many, context)
  File "django/db/backends/utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)
  File "django/db/utils.py", line 90, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "django/db/backends/utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)

This issue occurred specifically on CreateImage, but the same scenario can occur for CreateIIIFURL and CreateIIIFInformation: the existing image check does not use the primary database, so a stale read can occur where running the same API request twice could cause an IntegrityError. This was noticed due to some lag of unknown origin on the replica, starting from this weekend.