provide openapi document and link from homepage

[pvgenuchten]

Add an interactive openapi document at /ogcapi/openapi and link to it from /ogcapi

Links should be annotated as rel=service-desc && rel=service-doc, see example at https://demo.pygeoapi.io/master?f=json

• on /ogcapi page, create a link to /ogcapi/openapi
• /ogcapi/openapi?f=html should return the interactive api page
• /ogcapi/openapi?f=json should return the json encoded OAS document
• add /ogcapi/openapi itself to the openapi document
• add /ogcapi/conformance to the openapi document

[fxprunayre]

We will have to discuss how we build the global API of the microservices - how we can combine APIs from different services, how to "combine" with GN4 API ... We can start first by not building Java client from the not up to date yml document and build the openAPI using Springfox like in GN4.

Maybe we have to tag "extensions" so we can more easily follow what is core OGC API Records and what is GN specific.

[pvgenuchten]

In standup decided to not use central schema-files but generate with springfox

[fxprunayre]

Some of the fixes done in ffd9845