"Format:" in responses causes failure

[mzbik]

If you have a response schema that looks like:

      responses:
        400:
          description: Failure, see body
          content:
            application/json:
              schema:
                type: string
        '200':
          description: Successfully returning document
          content:
            application/pdf:
              schema:
                type: string
                format: email # ERROR

This will throw an error (unknown format "email" ignored in schema at path "#") unless you specify strictSchema = false. It appears that compileResponseValidationSchema in validation.js creates a bare Ajv instance without adding in known formats. See what is done in @fastify/ajv-compiler or fast-json-stringify when creating Ajv instances.