Write tests for Wallet model and authentication logic

[payton]

The title says it all.

[pconerly]

Similarly, it'd be great to have an example for how projects with django-siwe-auth should authenticate users in their unit tests.

We probably need a minimal python implementation of MetaMask's ECDSA key setup & signing.

[pconerly]

Oh, I think we can use the same tools that siwe-py used in their tests: https://github.com/spruceid/siwe-py/blob/main/tests/test_siwe.py mainly eth_account

[payton]

TODO:

1. Create tests for Wallet model
2. Create tests around SiweBackend

   django-siwe-auth/siwe_auth/backend.py

   Lines 41 to 45 in e43e76e

   	class SiweBackend(BaseBackend):
   	"""
   	Authenticate an Ethereum address as per Sign-In with Ethereum (EIP-4361).
   	"""