Discussion on zulip around how to do a plaintext search of DocumentReference content has come to the realization that the generic search parameter _content could be used to search the content (document bits) that are indexed by the DocumentReference resource. This use of _content should be made more clear.

Add a subsection on DocumentReference on text searching of content.

• Services may implement the _content search parameter such that it searches the DocumentReference.content.attachment.data and/or DocumentReference.content.attachment.url.

• Clients may use the _content search parameter to discover DocumentReference resources that have the searched term within their attachment

Question: Should this be expected of a server that declares (CapabilityStatement) support for _content search parameter with DocumentReference resources? Or is this extended support that should need further assertions in the CapabilityStatement?