Content-Crs and Content-Bbox headers

[joanma747]

Map response (requesting a map subset) metadata:

Req.
A. A map response SHALL include a "Content-Crs" header with the URI of the CRS used to render the map except if the content is in http://www.opengis.net/def/crs/OGC/1.3/CRS84

B. A map response SHALL include a "Content-Bbox" header with the actual geospatial boundary of the rendered map. The server should honor the subset request if it is present. The Content-Bbox coordinates SHALL be in "Content-Crs" CRS (output CRS) and shall honor the CRS order.

This goes to the BBOX-subset single requeriments class:
Permission: When the requested subset is outside the bounds of the requested CRS the server MAY limit the Content-Bbox to the valid values in the CRS (issue 85).

[joanma747]

Done in requirements/core/REQ_map-response.adoc[]
Done in recommendation/bbox/PER_map-outside-bounds.adoc[]