accessTokenRetrievalKey authentication; lifetimes + refresh?

[martin-helmich]

Affected URL

https://developer.mittwald.de/docs/v2/reference/user/user-authenticate-with-access-token-retrieval-key/

Describe the issue

The documentation is unclear in regards to the following questions:

• Does the expiresAt property refer to the access token or the refresh token?
• If the former, do (and if so, when) refresh tokens also expire?
• Which API operation should be used to use the refresh token? I'm presuming it's user-refresh-session, but it might be worth it to mention this explicitly.