Add wrappers for gRPC errors

[llucax]

What's needed?

We need to make sure gRPC errors are properly wrapped so we don't leak the use of grpc/protobuf to client users.

From frequenz-floss/frequenz-api-dispatch#144:

gRPC errors in Python are raised as grpc.RpcError exceptions. Here's how to handle them:

import grpc

try:
    response = await self._stub.GetMicrogridDispatch(request)
    # Process the successful response here

except grpc.RpcError as error:
    status_code = error.code()  # Get the gRPC status code
    details = error.details()   # Optional error details as a string 

    # Example of handling based on status code
    if status_code == grpc.StatusCode.NOT_FOUND:
        print("Resource not found!")
    elif status_code == grpc.StatusCode.PERMISSION_DENIED:
        print("Insufficient permissions")
    else: 
        print(f"Error occurred: {status_code} - {details}")

Proposed solution

Add wrapper error classes for the relevant gRPC errors raised by clients.

Some of these errors should inherit from specific Python built-in errors, like INVALID_ARGUMENT should inherit from ValueError, NOT_FOUND and ALREADY_EXISTS should probably inherit from KeyError, etc.

For errors that should never occur (because the client is doing some sanity checks to prevent them from happening), we should probably still have a wrapper in the client, like UnexpectedError, because a server could always misbehave for some reason.

When raising these errors in the client, we can still attach the original gRPC error using the raise OurClientError(...) from grpc_error syntax, which could be very useful for debugging purposes.

Additional context

• Document error response behavior frequenz-api-dispatch#144 (comment)

[llucax]

Done in:

• Add client exceptions #55