AJV $data support #920

[ZakRabe]

Issue

Add support for the AJV $data option to Foal configuration. Resolves #920

Solution and steps

• Add $data attribute to options passed to AJV initialization in getAjvInstance, defaulted to undefined
• Updated documentation in "Validation and Sanitization" to list the new configuration property.
• Added test to should accept custom configuration from the Config to test the case where $data is true. Tested both validation success and failure.
• Added test to getAjvInstance to test the default case where $data is undefined.
• Added test to check throwing a ConfigTypeError when settings.ajv.$data has an invalid type.

Checklist

• update/check docs (code comments and docs/ folder).
• update/check tests.
• Update/check the cli generators.

[LoicPoullain]

Thank you for taking care of this @ZakRabe and thank you for the style consistency of your tests. I added some notes below.

Also, to ensure that we have a stable product that is backwards compatible with previous versions, we should not add new defaults to the AJV instance configuration. Could you leave the default value $data as undefined? I guess this will require updating some of your tests.

[ZakRabe]

@LoicPoullain Thanks for the feedback.

Updated getAjvInstance to remove the default, and mirrored this change in the docs.
Updated the tests to remove the silly deepStrictEqual mistake, and added the missing $ back to the errors object.
Updated the tests to check that AJV cannot validate $data references by default, and can use them when $data is true in the custom configuration.
Cleaned up extra spacing and resolved trailing comma differences between the rest of the code in the test and my own.

[LoicPoullain]

🚀