When an app definition includes a !with-type directive which specifies a non-existant content type, then a problem should be shown in the definitions app and an error should be reported in the log.

Currently no problems are reported, and nothing shows up in the log.

This will help developers - for example when they make a simple typo in the content type name.

Acceptance criteria:

• Display a problem in the definitions app (Severity: Major)
• Log an error