CLI Token / Jottacloud follow up

[albertony]

Follow up from #7:

1. First commit adds support for v2 authid with cli tokens, which was simply skipped in Added support for Jottacloud cli token #7.
2. Second commit disables v2 authid for providers that uses refresh token rotation, since these are not (currently) compatible, if my understanding is correct! This is related to Disable automatic use of v2 authid for Jottacloud duplicati#4779 which prevents "auto-upgrade" from v1 to v2 authid in Jottacloud backend of Duplicati. The current change in oauth handler would also do the same, but also prevents explicit use of v2 authids, and is a more "consistent" solution. For more background, see Disable automatic use of v2 authid for Jottacloud duplicati#4779.
3. Third commit corrects (hopefully) the "fetch token" handling when using cli token, enabling automatic insert of the authid back into duplicati. (This fetch token thing was something I had a question about in the original pr, but never got an answer).

[jthall]

@albertony this now deployed at https://duplicati-oauth-handler-beta.appspot.com/

[albertony]

@kenkendk Any chance of getting this considered...?