fix: xblock error mfe unit preview (#1508)

* feat: add functionality to see unit draft preview

* fix: course redirect unit to sequnce unit redirect

* fix: not showing preview when masquerading

* feat: in preview fetch draft branch of sequence metadata

src/courseware/course/sequence/Sequence.jsx

@@ -204,7 +204,7 @@ const Sequence = ({
               sequenceId={sequenceId}
               unitId={unitId}
               unitLoadedHandler={handleUnitLoaded}
-              isStaff={isStaff}
+              isOriginalUserStaff={originalUserIsStaff}
             />
             {unitHasLoaded && renderUnitNavigation(false)}
           </div>

src/courseware/course/sequence/SequenceContent.jsx

@@ -15,7 +15,7 @@ const SequenceContent = ({
   sequenceId,
   unitId,
   unitLoadedHandler,
-  isStaff,
+  isOriginalUserStaff,
 }) => {
   const intl = useIntl();
   const sequence = useModel('sequences', sequenceId);
@@ -60,7 +60,7 @@ const SequenceContent = ({
       key={unitId}
       id={unitId}
       onLoaded={unitLoadedHandler}
-      isStaff={isStaff}
+      isOriginalUserStaff={isOriginalUserStaff}
     />
   );
 };
@@ -71,7 +71,7 @@ SequenceContent.propTypes = {
   sequenceId: PropTypes.string.isRequired,
   unitId: PropTypes.string,
   unitLoadedHandler: PropTypes.func.isRequired,
-  isStaff: PropTypes.bool.isRequired,
+  isOriginalUserStaff: PropTypes.bool.isRequired,
 };
 
 SequenceContent.defaultProps = {

src/courseware/course/sequence/Unit/index.jsx

@@ -22,7 +22,7 @@ const Unit = ({
   format,
   onLoaded,
   id,
-  isStaff,
+  isOriginalUserStaff,
 }) => {
   const { formatMessage } = useIntl();
   const [searchParams] = useSearchParams();
@@ -33,7 +33,7 @@ const Unit = ({
   const unit = useModel(modelKeys.units, id);
   const isProcessing = unit.bookmarkedUpdateState === 'loading';
   const view = authenticatedUser ? views.student : views.public;
-  const shouldDisplayUnitPreview = pathname.startsWith('/preview') && isStaff;
+  const shouldDisplayUnitPreview = pathname.startsWith('/preview') && isOriginalUserStaff;
 
   const getUrl = usePluginsCallback('getIFrameUrl', () => getIFrameUrl({
     id,
@@ -78,7 +78,7 @@ Unit.propTypes = {
   format: PropTypes.string,
   id: PropTypes.string.isRequired,
   onLoaded: PropTypes.func,
-  isStaff: PropTypes.bool.isRequired,
+  isOriginalUserStaff: PropTypes.bool.isRequired,
 };
 
 Unit.defaultProps = {