`BulkOperation.data` is required for `POST`, `PUT` and `PATCH`

[azmeuk]

RFC7644 indicates that BulkOperation.data is required for POST, PUT and PATCH:

  data  The resource data as it would appear for a single SCIM POST,
     PUT, or PATCH operation.  REQUIRED in a request when "method"
     is "POST", "PUT", or "PATCH".

There should be a validator for this.