Insert (not update) a member in a PATCH collection

[HeikoTheissen]

In PATCH collection requests, the control information "@etag": "*" can be used in a collection member to express that this shall be updated, but not inserted. This corresponds to the If-Match: * header.

What control information can be used if a collection member shall be inserted, not updated? This would correspond to the If-None-Match: * header. (It is not necessary to express arbitrary etag values here, only *.)