test coverage improvements; mTLS enforcement; agent broke :(

app/apps/keys/certificates.py

@@ -41,7 +41,7 @@ def issue_certificate_for_key(key: SSHKey, created_by=None) -> SSHCertificate:
     safe_name = _sanitize_label(key.name or "key")
     identity = f"keywarden-cert-{key.user_id}-{safe_name}-{key.id}"
     cert_text = _sign_public_key(
-        ca_private_key=ca.private_key,
+        ca_private_key=ca.get_private_key(),
         ca_public_key=ca.public_key,
         public_key=key.public_key,
         identity=identity,