Handle readonly mode

src/intl.ts

@@ -47,6 +47,9 @@ export const commonMessages = defineMessages({
   properties: {
     defaultMessage: "Properties"
   },
+  readOnly: {
+    defaultMessage: "Saleor runs in read-only mode. Changes not saved."
+  },
   requiredField: {
     defaultMessage: "This field is required"
   },

src/mutations.tsx

@@ -6,6 +6,7 @@ import { useIntl } from "react-intl";
 
 import useNotifier from "./hooks/useNotifier";
 import { commonMessages } from "./intl";
+import { maybe } from "./misc";
 
 export interface TypedMutationInnerProps<TData, TVariables> {
   children: (
@@ -32,9 +33,21 @@ export function TypedMutation<TData, TVariables>(
         mutation={mutation}
         onCompleted={onCompleted}
         onError={(err: ApolloError) => {
+          if (
+            maybe(
+              () =>
+                err.graphQLErrors[0].extensions.exception.code ===
+                "ReadOnlyException"
+            )
+          ) {
+            notify({
+              text: intl.formatMessage(commonMessages.readOnly)
+            });
+          } else {
             notify({
               text: intl.formatMessage(commonMessages.somethingWentWrong)
             });
+          }
           if (onError) {
             onError(err);
           }

src/queries.tsx

@@ -82,7 +82,7 @@ export function TypedQuery<TData, TVariables>(
             skip={skip}
             context={{ useBatching: true }}
           >
-            {queryData => {
+            {(queryData: QueryResult<TData, TVariables>) => {
               if (queryData.error) {
                 pushMessage({
                   text: intl.formatMessage(commonMessages.somethingWentWrong)