[api] fix migration failure
[api] fix db:setup failure without running backend
[webui] make sure to check if source access is allowed in #show
[api] fix db:setup in a sane way
[api] ensure that release requests can not get opened when stopped patchinfos exist

this worked when former successful builds happened.
[api] trying to make the event class autoloading less fragile
[webui] replace project_or_package_link partial with a helper function

This allows much saner programming than in erb