feat: added generic json payload decoder function

internal/api/request/json.go

@@ -0,0 +1,20 @@
+package request
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+)
+
+func DecodeJSON[T any](r *http.Request) (T, error) {
+	var payload T
+
+	decoder := json.NewDecoder(r.Body)
+	decoder.DisallowUnknownFields()
+
+	if err := decoder.Decode(&payload); err != nil {
+		return payload, fmt.Errorf("error decoding payload: %w", err)
+	}
+
+	return payload, nil
+}