Note multiple API endpoint base paths in spec.yaml

[michielbdejong]

In spec.yaml we define:

• https://<discovery-fqdn>/.well-known/ocm
• https://<discovery-fqdn>/ocm-provider
• https://<ocm-fqdn>/<ocm-base-path>/shares
• https://<ocm-fqdn>/<ocm-base-path>/notifications
• https://<ocm-fqdn>/<ocm-base-path>/invite-accepted

(<discovery-fqdn> = is an OCM server's <fqdn> or fallback to whatever FQDN its SRV DNS record redirects to)
(<ocm-fqdn> and <ocm-base-path> come from discovery endPoint value)

We should make it clear that the two discovery endpoints live on a different base URL than the three API endpoints.

[glpatcern]

This was closed at some stage, the spec now mentions discovery-fqdn only.