Iframe should support input variables (#5156)

### What problem does this PR solve?

Right now we cannot embed a chat in website when it has variables in the
begin component.
This PR tries to read the variables values from the query string via a
data_ prefixed variable.

#5016 

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

---------

Co-authored-by: gstrat88 <gstrat@innews.gr>

web/src/pages/flow/header/index.tsx

@@ -9,7 +9,7 @@ import { useCallback } from 'react';
 import { Link, useParams } from 'umi';
 import {
   useGetBeginNodeDataQuery,
-  useGetBeginNodeDataQueryIsEmpty,
+  useGetBeginNodeDataQueryIsSafe,
 } from '../hooks/use-get-begin-query';
 import {
   useSaveGraph,
@@ -35,7 +35,7 @@ const FlowHeader = ({ showChatDrawer, chatDrawerVisible }: IProps) => {
   const getBeginNodeDataQuery = useGetBeginNodeDataQuery();
   const { showEmbedModal, hideEmbedModal, embedVisible, beta } =
     useShowEmbedModal();
-  const isBeginNodeDataQueryEmpty = useGetBeginNodeDataQueryIsEmpty();
+  const isBeginNodeDataQuerySafe = useGetBeginNodeDataQueryIsSafe();
 
   const handleShowEmbedModal = useCallback(() => {
     showEmbedModal();
@@ -79,7 +79,7 @@ const FlowHeader = ({ showChatDrawer, chatDrawerVisible }: IProps) => {
           <Button
             type="primary"
             onClick={handleShowEmbedModal}
-            disabled={!isBeginNodeDataQueryEmpty}
+            disabled={!isBeginNodeDataQuerySafe}
           >
             <b>{t('embedIntoSite', { keyPrefix: 'common' })}</b>
           </Button>