Accept header for /search requests?

[m-mohr]

The specification says at https://github.com/radiantearth/stac-api-spec/tree/main/item-search for Item Search:

This search link relation must have a type of application/geo+json. If no method attribute is
specified, it is assumed to represent a GET request. If the server supports both GET and POST requests, two links should be included, one with a method of GET one with a method of POST.

Other links with relation search may be included that advertise other content types the server may respond
with, but these other types are not part of the STAC API requirements.

This is good, but it implies that the client may need to send an Accept: application/geo+json header because otherwise the server doesn't know which of the search link the client has selected. This is not overly clear in the spec and should probably be improved.

Related issue: opengeospatial/ogcapi-features#832