Relevant endpoints: GET, POST /content/types/{contentTypeId}

Steps to reproduce

1. Create a content type according to IBX-5931 description
2. Try
   • loading content type through REST
   • creating content type with SEO field type through REST

Actual result

SEO metadata is not loaded, REST consumer is unable to input metadata when creating SEO field definition.

Expected result

It's possible to see SEO metadata in REST content type GET response and it's possible to set them when creating or updating content type via POST endpoint.