Add customer management

internal_frontend/lib/api/callApi.ts

@@ -0,0 +1,28 @@
+// lib/api/callApi.ts
+import {serverCall} from "@/lib/api/serverCall";
+
+export async function callApi<TResponse, TRequest = unknown>(
+    path: string,
+    method: "GET" | "POST" | "PUT" | "DELETE" | "PATCH",
+    body?: TRequest
+): Promise<TResponse> {
+    const res = await serverCall(path, method, body);
+
+    const contentType = res.headers.get("content-type") ?? "";
+    const isJson = contentType.includes("application/json");
+
+    const rawBody = isJson ? await res.json() : await res.text();
+
+    console.log(`[api ${path}] Response:`, res.status, rawBody);
+
+    if (!res.ok) {
+        const errorMessage = isJson
+            ? (rawBody?.message ?? rawBody?.errors?.join(", ")) ?? "Unbekannter Fehler"
+            : String(rawBody);
+
+        console.error(`[api ${path}] Error:`, errorMessage);
+        throw new Error(errorMessage);
+    }
+
+    return rawBody as TResponse;
+}