Implement a validator (checker) for the Biff Catalog Model (PUP-2029).
This ticket is about creating the first cut of a checker (similar to the checker for the Puppet::Pops::Model checker) and configuring the infrastructure to enable validation and reporting of issues.
To test the validator, some simple intrinsic validation rules can be implemented with corresponding structured issues:
- SourceReference must contain a valid UR
- Location must contain a valid URI fragment
- A realized resource must have a realized_at Location
(Additional Validation to be added later)