Clarify: Send token to discovery endpoints

[m-mohr]

Discovery endpoints (e.g. GET /collections) allow to be requested with and without Bearer Token.
Sending the Bearer Tokens with the clients is important once you have it so that private data (e.g. Collections) can be requested.
This is important for e.g. exposing Planet data through openEO Platform.

Clarify in the API that clients should send tokens if available. This will likely result in issues for all clients, none supports this yet AFAIK.

[m-mohr]

• Clarify in API spec: Clarify: Send token to discovery endpoints #416 #417
• Open Python client issue: Clear capabilities cache on log in openeo-python-client#254, Bearer token is sent
• Open R client issue - R client sends token, but needs to refresh process cache on authentication: Refresh cached processes and collection after separate login openeo-r-client#83
• Open JS client issue - Refresh cache after login openeo-js-client#55
• Open Web Editor issue - Re-request discovery endpoints after login openeo-web-editor#218

[flahn]

The openeo r client already supports this feature for processes and collections. It was requested during openEO to allow internal staff to access the full data catalogue and offer published collections to external users.

[m-mohr]

@flahn This is great news. Is there any caching implemented in the R client that would need to be refreshed on authentication changes?