feat(rest): autoplace returns LINSTOR-shaped success ApiCallRc

Java LINSTOR replies with a `[]ApiCallRc` body that carries
MASK_INFO + RC_RSC_DFN_PLACED. golinstor.Autoplace ignored an empty
200, but CLI tools and proxies that surface API messages expect the
shape to match. Emit it.

Co-Authored-By: Claude <noreply@anthropic.com>
Signed-off-by: Andrei Kvapil <kvapss@gmail.com>

Author: kvaps

pkg/rest/autoplace.go

@@ -130,9 +130,25 @@ func (s *Server) handleAutoplace(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	w.WriteHeader(http.StatusOK)
+	// Java LINSTOR replies with a `[]ApiCallRc` envelope on success.
+	// golinstor's RD.Autoplace ignores an empty body, but tools that
+	// surface API messages (e.g. the linstor CLI) want a real result
+	// to log. Return MASK_INFO + RC_PLACEMENT_DONE-style entry so the
+	// shape matches the oracle's.
+	writeJSON(w, http.StatusOK, []apiv1.APICallRc{{
+		RetCode: apiCallRcInfo | apiCallRcRDAutoplaceDone,
+		Message: "Resource definition '" + rdName + "' auto-placed",
+	}})
 }
 
+// apiCallRcInfo is upstream LINSTOR's MASK_INFO bit (0x0040_…).
+// Combined with a per-action code it lets clients distinguish
+// success-with-info from a fatal error.
+const (
+	apiCallRcInfo            int64 = 0x0040_0000_0000_0000
+	apiCallRcRDAutoplaceDone int64 = 0x4231 // ApiConsts.RC_RSC_DFN_PLACED
+)
+
 // placeResources picks free pools from the candidates and creates Resource
 // objects up to filter.PlaceCount. Returns (placed, want, err).
 func (s *Server) placeResources(ctx context.Context, rdName string, filter *apiv1.AutoSelectFilter) (int, int, error) {