When a user adds a sitelink in the wrong "format" such as
sitelinks: { "afwiki": "a string" }
instead of responding with a generic 500 error we should have a specific error.
Acceptance criteria:
- For PUT the error code will be 400 and for PATCH it will be 422
- Error message will read:
{ "code": "invalid-sitelink-type", "message": "Not a valid sitelink type" }