[server][ogcapi] various enhancements including feature schema support

[elpaso]

Various OAPIF improvements and updates including support for collections /schema endpoint

Partial implementation of QEP 414 - QGIS Server OAPIF JSON-FG and FlatGeobuf formats https://github.com/qgis/QGIS-Enhancement-Proposals/blob/master/qep-414-server-oapif-jsonfg-flatgeobuf.md

Main new features:

• schema (including x-ogc-role , format and type for main widgets)
• references (from RelationReference and ValueRelation)
• profiles (for references)
• full crs support in requests and responses (includes storageCrs and storageCrsCoordinateEpoch if available)
• extra geometry columns support (Postgres), exposed as WKT (transformed to the requested CRS)
• codelist for enums and ValueMap

Funded by: Geogirafe user group / OPENGIS.ch

New conformance classes:

    // From https://docs.ogc.org/is/19-072/19-072.html
    "http://www.opengis.net/spec/ogcapi-common-1/1.0/req/landing-page",
    "http://www.opengis.net/spec/ogcapi-common-1/1.0/req/oas30",
    "http://www.opengis.net/spec/ogcapi-common-1/1.0/req/html",
    "http://www.opengis.net/spec/ogcapi-common-1/1.0/req/json",

    // From https://docs.ogc.org/is/23-058r2/23-058r2.html
    "http://www.opengis.net/spec/ogcapi-common-3/1.0/conf/schemas",
    "http://www.opengis.net/spec/ogcapi-common-3/1.0/conf/profile-parameter",
    "http://www.opengis.net/spec/ogcapi-common-3/1.0/conf/profile-references",
    "http://www.opengis.net/spec/ogcapi-common-3/1.0/conf/profile-codelists",
    "http://www.opengis.net/spec/ogcapi-common-3/1.0/conf/advanced-property-roles",
    "http://www.opengis.net/spec/ogcapi-common-3/1.0/conf/references",
    "http://www.opengis.net/spec/ogcapi-common-3/1.0/conf/returnables-and-receivables",

    // From: https://docs.ogc.org/is/18-058r1/18-058r1.html
    "http://www.opengis.net/spec/ogcapi-features-2/1.0/conf/crs",

    // From: https://docs.ogc.org/is/17-069r4/17-069r4.html
    "http://www.opengis.net/spec/ogcapi-features-1/1.0/conf/core",
    "http://www.opengis.net/spec/ogcapi-features-1/1.0/conf/oas30",
    "http://www.opengis.net/spec/ogcapi-features-1/1.0/conf/html",
    "http://www.opengis.net/spec/ogcapi-features-1/1.0/conf/geojson",

    // From: https://docs.ogc.org/is/19-079r2/19-079r2.html
    // TODO: queryables and sortables are not supported yet, but we may want to add them in the future:
    // requirement http://www.opengis.net/spec/ogcapi-features-3/1.0/req/queryables-query-parameters
    // filtering has limited supported but we cannot advertise it yet because of the dependency on
    // queryables-query-parameters:
    // http://www.opengis.net/spec/ogcapi-features-3/1.0/conf/features-filter
    // http://www.opengis.net/spec/ogcapi-features-3/1.0/conf/filter

    // From part 3 https://docs.ogc.org/is/23-058r2/23-058r2.html
    "http://www.opengis.net/spec/ogcapi-features-5/1.0/conf/schemas",
    "http://www.opengis.net/spec/ogcapi-features-5/1.0/conf/profile-codelists",
    "http://www.opengis.net/spec/ogcapi-features-5/1.0/conf/profile-parameter",
    "http://www.opengis.net/spec/ogcapi-features-5/1.0/conf/feature-references",