Adding policy fails incorrectly when appId string length > 50

[KevinJCross]

When creating a policy with an app id >50 char the DB fails with "pq: value too long for type character varying(50)" and we return 500 intead of a 400 and message appId too long.

[joergdw]

I assume that “app id” means “App-GUID” which can not be longer than 36 characters. We could perhaps improve the error messaging here, catch these cases and return another message different from 500.