UniqueConstraintViolationException inside log when adding trusted servers using testing api

[skshetry]

Sample log from https://drone.owncloud.com/owncloud/phoenix/7515/24/13:

{"reqId":"2gbt7aFeIjaM3FErZKjb","level":3,"time":"2020-01-03T06:48:02+00:00","remoteAddr":"172.23.0.10","user":"admin","app":"PHP","method":"POST","url":"\/ocs\/v2.php\/apps\/testing\/api\/v1\/trustedservers?format=json","message":"Doctrine\\DBAL\\Exception\\UniqueConstraintViolationException: An exception occurred while executing 'INSERT INTO `oc_trusted_servers` (`url`, `url_hash`) VALUES(?, ?)' with params [\"http:\\\/\\\/owncloud\", \"668b5fcda851fe516fef14e82973beffe32f385a\"]:\n\nSQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '668b5fcda851fe516fef14e82973beffe32f385a' for key 'url_hash' at \/var\/www\/owncloud\/server\/lib\/composer\/doctrine\/dbal\/lib\/Doctrine\/DBAL\/Driver\/AbstractMySQLDriver.php#55"}

Analysis

This happens because we never check if the trusted server is already added. We just catch this error and return happily (which we should). The better way would be to check if the trusted server exists in the DB and then, make a decision (i.e. add or do nothing).
This pollutes the log, and could make debugging harder when checking CI failures.