implement exchange settings management and fallback rate handling

apps/edr-freight-web/backoffice/src/hooks/useExchangeSettings.ts

@@ -0,0 +1,34 @@
+import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
+import { useTranslation } from "react-i18next";
+import { toast } from "sonner";
+
+import { exchangeSettingsService } from "@/services/exchangeSettings.service";
+import { useErrorHandler } from "@/shared/hooks/useErrorHandler";
+
+const QUERY_KEY = ["exchangeSettings"];
+
+export const useExchangeSettingsQuery = () =>
+  useQuery({
+    queryKey: QUERY_KEY,
+    queryFn: () => exchangeSettingsService.get(),
+    // Feed health is only interesting while it is being looked at.
+    staleTime: 30_000,
+    refetchOnWindowFocus: true,
+  });
+
+export const useSetExchangeFallbackRate = () => {
+  const queryClient = useQueryClient();
+  const { t } = useTranslation();
+  const { handleError } = useErrorHandler(t);
+
+  return useMutation({
+    mutationFn: (rate: number) => exchangeSettingsService.setFallbackRate(rate),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: QUERY_KEY });
+      toast.success(
+        t("exchangeSettings.updated", "Fallback exchange rate updated"),
+      );
+    },
+    onError: handleError,
+  });
+};