Error messages should reference a generic signed token, not specifically the ID token

[bradydean]

The SignatureVerifier class is used to verify any signed token, not just ID tokens.
I think the error messages should reflect that.

auth0-python/auth0/v3/authentication/token_verifier.py

Lines 58 to 67 in f6925b6

	try:
	header = jwt.get_unverified_header(token)
	except jwt.exceptions.DecodeError:
	raise TokenValidationError("ID token could not be decoded.")
	alg = header.get('alg', None)
	if alg != self._algorithm:
	raise TokenValidationError(
	'Signature algorithm of "{}" is not supported. Expected the ID token '
	'to be signed with "{}"'.format(alg, self._algorithm))

[lbalmaceda]

Thanks, I agree with the proposed changes. Is that something you'd like to contribute with your own PR? Otherwise, we can take it. It would imply updating the exception messages to use "token" instead of "ID token", and probably fix the tests that are checking those messages.

Let me know.