Implement validation on Trust V3 API

Use JSONschema on create operations on V3 Trust API.

This change refactors a lot of the test_v3_auth tests to get them to
pass with proper validation.

Closes-Bug: #1362344
bp: api-validation

Change-Id: If4b59a6ac84e308eff8bf5ea35772173b0ba7fe5
Merge "Implement validation on Trust V3 API"