Validate data against a schema

Changes for 0.578 - 2023-12-29T23:13:44Z

• remove use of JSON::MaybeXS, to avoid potential use of JSON:🤐S; now we use Cpanel::JSON:🤐S or JSON:😛P directly, using the same environment variables as in Mojo::JSON for customization.
• new helper interface, get_document()