make some config parts optional

api/kiwi_vpn_api/config.py

@@ -227,8 +227,8 @@ class CryptoConfig(BaseModel):
     schemes: list[str] = ["bcrypt"]
 
     # pki settings
-    cert_algo: CertificateAlgo
-    expiry_days: int
+    cert_algo: CertificateAlgo | None
+    expiry_days: int | None
 
     @property
     def context(self) -> CryptContext:
@@ -246,7 +246,7 @@ class Config(BaseModel):
     # common name for the server
     server_name: str
     # may include client-to-client, cipher etc.
-    openvpn_extra_options: dict[str, Any]
+    openvpn_extra_options: dict[str, Any] | None
 
     db: DBConfig
     jwt: JWTConfig