feat: Amend status codes in SDF server

[johnrwatson]

Adds catches for a lot of missing/improve status 500 throws within sdf.

I've tried to leave a few groups at 500 still:

• DAL errors
• Postgres/third party connection errors
• Other things that genuinely should throw, like your workspace is broken

I'm still to do Session and Qualification, I'll follow up on those.