[WFS] Produce warning in WFS GetCapabilities if fid not provided

[dmorissette]

The WFS spec requires that a service provide a fid attribute on the features
returned by GetFeature (gml:id in GML3). The attribute to use as the fid can be
specified in MapServer using the wfs/gml_featureid metadata.

Some WFS clients refuse to interact with MapServer's WFS if the fid is not
provided. To facilitate the life of people deploying WFS services, I would like
to add a warning in the WFS GetCapabilities response if the wfs/gml_featureid
metadata is not specified.

I will add that warning in 4.9 if I hear no objections.

[sdlime]

Sounds ok to me.

Steve

[dmorissette]

Done in 4.9/4.10.

Added the following warning in GetCapabilities if ???_featureid metadata is not set:

<!-- WARNING: Feature Id attribute (fid) not specified for this feature type.
Make sure you set one of wfs_featureid, ows_feature_id or gml_featureid
metadata.  -->