`id_token` generation does not work with `EdDSA`

[azmeuk]

It seems id_token generation is broken with EdDSA jwks.

The create_half_hash method is called in the generate_id_token method:

authlib/authlib/oidc/core/grants/util.py

Lines 102 to 107 in c9890da

	if code:
	payload["c_hash"] = to_native(create_half_hash(code, alg))
	access_token = token.get("access_token")
	if access_token:
	payload["at_hash"] = to_native(create_half_hash(access_token, alg))

However, it seems it does not support EdDSA keys:

>>> from authlib.oidc.core.util import create_half_hash
>>> assert create_half_hash("test", "RS256")
>>> assert create_half_hash("test", "EdDSA")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AssertionError

After investigation, it seems this is because authlib tries to access hashlib.shaDSA, which does not exist:

authlib/authlib/oidc/core/util.py

Lines 7 to 14 in c9890da

	def create_half_hash(s, alg):
	hash_type = f"sha{alg[2:]}"
	hash_alg = getattr(hashlib, hash_type, None)
	if not hash_alg:
	return None
	data_digest = hash_alg(to_bytes(s)).digest()
	slice_index = int(len(data_digest) / 2)
	return urlsafe_b64encode(data_digest[:slice_index])