"try to control ... with pi service" should tolerate objects already under PI control

Description

When using the command
"try to control ... with pi service ..."
I have to know which objects are currently not under PI control.

Otherwise I get the exception
Caused by: org.postgresql.util.PSQLException: ERROR: duplicate key value violates unique constraint "ukjevjp7l6m7banvyg5rw7ms3y4"
Detail: Key (identifier, type)=(urn:nbn:de:hbz:464-20190219-145710-2, dnbUrn) already exists.

PI service should tolerate objects that are already under its control and just skip

Environment

None

Assignee

Sebastian Hofmann

Reporter

Frank L├╝tzenkirchen

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Components

Fix versions

Priority

Medium
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