[FEATURE] Implement logic to validate detector type

[dbwiddis]

Is your feature request related to a problem?

Implement the logic from this method into the placeholder REST request handler created in #221 for the validate detector handler.

What solution would you like?

This should be mostly a copy/paste exercise. However, note there may be overlap between this and create detector, and combine methods when possible to respect DRY principle.

[dbwiddis]

Superceded by #353