fix: details are optional in API errors (#411)

The ansible integrations tests for `certificate_info` were silently
failing because the `details` was missing from the API error.


https://dev.azure.com/ansible/hetzner.hcloud/_build/results?buildId=116526&view=logs&j=790943b1-2131-5e64-166b-e241853dcaf1&t=4ad41445-2459-50a0-f330-095184dc0a34&l=641

hcloud/_client.py

@@ -247,7 +247,7 @@ def request(  # type: ignore[no-untyped-def]
             raise APIException(
                 code=error["code"],
                 message=error["message"],
-                details=error["details"],
+                details=error.get("details"),
                 correlation_id=correlation_id,
             )
 

tests/unit/test_client.py

@@ -110,7 +110,6 @@ def test_request_fails_correlation_id(self, client, response):
                 "error": {
                     "code": "conflict",
                     "message": "some conflict",
-                    "details": None,
                 }
             }
         ).encode("utf-8")