Do we need RESTCONF depth/fields filters?

[cabo]

(Andy Bierman, https://mailarchive.ietf.org/arch/msg/core/XLv4ZusZubBrJPC5aW7UqqeHrxw)

The client must know all of the key values in advance
before being able to use the SID of a data node
in a FETCH request. It is difficult and expensive
to retrieve the entire datastore contents at once,
just to discover the key values in use for the YANG list
entries within the datastore.

RESTCONF has the 'depth' and 'fields' filter parameters
to address this issue. NETCONF has subtree and XPath filtering.
NETCONF servers can generally support selection of 1 value or all
values, for each key.

Perhaps CORECONF will need the 'depth' filter parameter.