Mint: Use Pydantic validated BaseModel for Lightning API responses

[callebtc]

Currently, this is our pattern throughout the lightning backends:

        try:
            r = await self.client.get(url=f"{self.endpoint}/api/v1/wallet", timeout=15)
            r.raise_for_status()
        except Exception as exc:
            return StatusResponse(
                error_message=f"Failed to connect to {self.endpoint} due to: {exc}",
                balance=0,
            )

        try:
            data: dict = r.json()
        except Exception:
            return StatusResponse(
                error_message=(
                    f"Received invalid response from {self.endpoint}: {r.text}"
                ),
                balance=0,
            )

We should make use of pydantic and predefine all expected response models from the Lightning backends so we can automatically validate the response. This would get rid of a lot of boilerplate and error checking in the code and make things a lot more robust and less prone to human errors.