[MM-64360] Data retention: optionally preserve pinned posts (#31165)

* add new config to preserve pinned posts during data retention

* more graceful error if the pinned post was a reply in a deleted thread

webapp/channels/src/components/error_page/error_message.tsx

@@ -60,6 +60,16 @@ const ErrorMessage: React.FC<Props> = ({type, message, service, isGuest}: Props)
                 </p>
             );
             break;
+        case ErrorPageTypes.POST_NOT_FOUND:
+            errorMessage = (
+                <p>
+                    <FormattedMessage
+                        id='post.error.access'
+                        defaultMessage="The post you're requesting is private or does not exist."
+                    />
+                </p>
+            );
+            break;
         case ErrorPageTypes.CLOUD_ARCHIVED:
             errorMessage = (
                 <p>

webapp/channels/src/components/error_page/error_title.tsx

@@ -31,6 +31,14 @@ const ErrorTitle: React.FC<Props> = ({type, title}: Props) => {
                 />
             );
             break;
+        case ErrorPageTypes.POST_NOT_FOUND:
+            errorTitle = (
+                <FormattedMessage
+                    id='post.error.title'
+                    defaultMessage='Post Not Found'
+                />
+            );
+            break;
         case ErrorPageTypes.CLOUD_ARCHIVED:
             errorTitle = (
                 <FormattedMessage

webapp/channels/src/components/permalink_view/actions.ts

@@ -52,6 +52,11 @@ function focusReplyPost(post: Post, channel: Channel, teamId: string, returnTo:
     return async (dispatch, getState) => {
         const {data} = await dispatch(getPostThread(post.root_id));
 
+        if (!data) {
+            getHistory().replace(`/error?type=${ErrorPageTypes.POST_NOT_FOUND}&returnTo=${returnTo}`);
+            return {data: false};
+        }
+
         if (data!.first_inaccessible_post_time) {
             getHistory().replace(`/error?type=${ErrorPageTypes.CLOUD_ARCHIVED}&returnTo=${returnTo}`);
             return {data: false};

webapp/channels/src/i18n/en.json

@@ -5008,6 +5008,8 @@
   "post.ariaLabel.reaction": ", 1 reaction",
   "post.ariaLabel.reactionMultiple": ", {reactionCount} reactions",
   "post.ariaLabel.replyMessage": "At {time} {date}, {authorName} replied, {message}",
+  "post.error.access": "The post you're requesting is private or does not exist.",
+  "post.error.title": "Post Not Found",
   "post.reminder.acknowledgement": "You will be reminded at {reminderTime}, {reminderDate} about this message from {username}: {permaLink}",
   "post.reminder.systemBot": "Hi there, here's your reminder about this message from {username}: {permaLink}",
   "post.renderError.message": "An error occurred while rendering this post.",

webapp/channels/src/utils/constants.tsx

@@ -927,6 +927,7 @@ export const ErrorPageTypes = {
     PERMALINK_NOT_FOUND: 'permalink_not_found',
     TEAM_NOT_FOUND: 'team_not_found',
     CHANNEL_NOT_FOUND: 'channel_not_found',
+    POST_NOT_FOUND: 'post_not_found',
     CLOUD_ARCHIVED: 'cloud_archived',
 };