Add validation constraints to config schema

Here's a first pass without the update tests, which I'm still working on. I want to see how this MR works out first.

This makes almost all the schema fully validatable, with the exception of the sequence declaration which I don't know how to fix. Core doesn't seem to have any examples of this either.

This limits tags to 32 characters, but I will probably change that to a different validation because it seems too restrictive even though in practice this should be quite sufficient.