Support for versions of JSON Schema

[russormes]

What

The ajv lib does not now support json-schema-draft-06 out of the box, moving to json-schema-draft-07. This requires that we load the meta-schema to support 06.

Should we support older versions of the schema definition and offer a config option to select an older meta-schema?

class JSONValidator {
	constructor(schemas, options) {
	this.options = options;
	this.ajv = new AJV(options);

	const schemaVersion = options.schemaVersion;
	if (schemaVersion) {
		const metaSchema = require(`ajv/lib/refs/json-schema-draft-${schemaVersion}.json`);
		this.ajv.addMetaSchema(metaSchema);
	}
	if (schemas) {
		this.addSchema(schemas);
	}
}