Fix: ecdsa token verify

[amalcaraz]

A fix for the issue in the verify_signature function at src/aleph/toolkit/ecdsa.py:70.

The Problem:

public_key = PublicKey.from_hex(public_key_hex)  # This method doesn't exist

The Fix:

public_key = PublicKey(bytes.fromhex(public_key_hex))  # Correct way to create PublicKey

What was happening:

• When verify_auth_token called verify_signature, it would throw an AttributeError because PublicKey.from_hex() doesn't exist in the coincurve library
• The exception was caught by the except Exception: block and returned False
• So verify_auth_token always returned False, even with valid tokens and matching keypairs