Add credit usage simulation

[davidotte]

Change Description

Try to be precise. You can additionally add comments to your PR, this might help the reviewer a lot.

Add credit usage simulation for TabPFN extensions. For usage just import with from tabpfn_client.mock_prediction import check_api_credits and add decorator @check_api_credits to a function. Then, this function will first be simulated (both the execution time and credit usage), it will be checked if the estimated credit usage exceeds the current credits of the user. If yes an error is raised, if not the function gets normally executed.

Few notes:

• With adding a latency offset of 1s for each request, in my tests the simulated cost always overestimated the actual credit usage a bit, so this seems to work quite well. However, I don't know if other users will experience a significantly lower latency.
• For using the decorator in an extension, we probably have to create a common decorator for both client and tabpfn that simply does nothing if tabpfn-client is not used.
• I slightly changed the get_api_usage function Anshul implemented, such that the string for user info is created at config level and not at client level. This allows me to directly access these values.

If you used new dependencies: Did you add them to requirements.txt?

Who did you ping on Mattermost to review your PR? Please ping that person again whenever you are ready for another review.

@noahho

Breaking changes

If you made any breaking changes, please update the version number.
Breaking changes are totally fine, we just need to make sure to keep the users informed and the server in sync.

Does this PR break the API? If so, what is the corresponding server commit?

no

Does this PR break the user interface? If so, why?

no

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[noahho]

Great, this looks like a nice solution! Please add some more comments and take a look at my suggestions

[noahho]

please only take a look at the one comment

[noahho]

Great, LGTM!