Optionaldata: IFieldRightsOptionalisTrue when the session is read-only, so no write operations are possible regardless of the granted rights.
OptionalrightsThe rights granted to the trustee on the field.
Optional_data: anyOptionaldata: anyStaticfromJS
A trustee's rights to a template field definition. Depending on the aclOnly option on the request, these are either the effective rights (the net result after group membership, allow/deny resolution, and the repository's privilege overlay) or the rights granted by the field's access control list alone.