Exception cleanup

[shsms]

What's needed?

All exceptions raised by the client need to be subclasses of ApiClientError. For non-grpc error, we could have an additional subclass called TradingClientError.

Then the documentation need be updated to say that users can catch all client exceptions by just catching ApiClientError.

Proposed solution

No response

Use cases

No response

Alternatives and workarounds

No response

Additional context

No response

[matthias-wende-frequenz]

@shsms can we close this issue?

[shsms]

I don't think this was ever done. Maybe keep as a good first issue for future team members?