Enhancement / Print “accessing as <user>” in client

[EvgeniLeonti]

notion ticket: https://www.notion.so/dagshub/Print-accessing-as-user-in-client-92af32ddfce2477ba7184722634fb891?pvs=4

[dagshub]

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[EvgeniLeonti]

@kbolashev i have implemented initial version which works fine, but isn't efficient:
it will make another http request to get the username from the token.

in cases where we call is_valid_token(), this new http request can be skipped.

so we have 2 options, leave it as is, or make required adjustments to skip the redundant http call.
in order to achieve the 2nd option, i thought about:

1. adding username to __token_cache
2. maintain existing caches to support backwards compatibility (adding username to already existing tokens)

this will require more complicated logic, and i'm not sure the scope of this task covers that.

WDYT?

[kbolashev]

I think you can change the signature and name of is_valid_token to return the username and get 99% of the way there.
You'll only have to call it for the case of the EnvVar token and that's it.

Turn it into get_username_of_token(token, host) -> Optional[str], return None if it fails, returns "login" otherwise.

[kbolashev]

Looks great!

I left a bunch of minor things that need to be changed, but the logic is great.

[kbolashev]

Congrats on the first feature PR for the client!!! 🥳