make Key class in python also use the new interface

Signed-off-by: Berend Sliedrecht <sliedrecht@berend.io>

wrappers/python/aries_askar/key.py

@@ -1,10 +1,10 @@
 """Handling of Key instances."""
 
-from typing import Union
+from typing import Union, Optional
 
 from . import bindings
 from .bindings import AeadParams, Encrypted, LocalKeyHandle
-from .types import KeyAlg, SeedMethod
+from .types import KeyAlg, KeyBackend, SeedMethod
 
 
 class Key:
@@ -15,8 +15,8 @@ def __init__(self, handle: LocalKeyHandle):
         self._handle = handle
 
     @classmethod
-    def generate(cls, alg: Union[str, KeyAlg], *, ephemeral: bool = False) -> "Key":
-        return cls(bindings.key_generate(alg, ephemeral))
+    def generate(cls, alg: Union[str, KeyAlg], *, key_backend: Optional[KeyBackend] = None, ephemeral: bool = False) -> "Key":
+        return cls(bindings.key_generate(alg, key_backend, ephemeral))
 
     @classmethod
     def from_seed(