Web metadata ows_schemas_location is not respected for OGC API Features, and appears to not be documented

[ejn]

It looks like the references to the OGC API yaml schema files are currently hardcoded to http://schemas.opengis.net here

For other services there is / should be a (currently undocumented?) web metadata ows_schema_location (see reference in the change log and reference in code (note type in comment!)).

At the very least, hardcoding a http:// link prevents a browser parsing the linked schema when the OGC API service itself is running on https:// such that it should be considered to change all references to OGC schema files to default to https://, but that is outside the scope of this ticket.

TODOs:

• The OGC API Features service should use the setting from ows_schema_location to reference the OGC yaml schemas
• ows_schema_location should be documented

[ejn]

I guess the solution is to use msOWSGetSchemasLocation() in processApiRequest().

[ejn]

ows_schemas_location is sufficiently documented for the other services (e.g. https://www.mapserver.org/ogc/wms_server.html#index-21), just my search-skills let me down - once the PR for the docs for OGC API is merged then no more action should be required here.

[ejn]

Now I realised why I didn't find the documentation for the other services: The parameter name is ows_schemas_location (note plural schemas), and not ows_schema_location as recorded in the old changelog entry.

Irritatingly my new commit also records adding support for ows_schema_location for OGC API, but hopefully this comment may help any users in the future who are as confused as I was.