MM-39710: saved posts screen and DB (#6020)

* MM-39710: saved posts screen and DB

- Adds ids of saved posts to the systems table, as we do with recent
mentions.
- Adds a new remote action to fetch saved posts (getFlaggedPosts).
- Adds a new screen to display those in a mobile.
- Displays saved posts in the tablet view next to profile card.

* Uses Preferences instead of System table

Renames to saved posts wherever possible

* Adds text to localization file

* Fixes fetching/saving saved posts

* Refactor mini post to components folder

* Fixes hooks dependencies according to review

* Removes unnecessary 'withObservables'

* Small refactor

* Satisfies linter

* Adds empty state

And fixes empty state icon to be theme sensitive.
Both recent_mentions and saved_posts.

* Fixes empty screen's alignment

* Add missing preference

* add missing translation strings

* remove unused database type definition

* Fetch newly saved post

* Fix return type for client.getSavedPosts

* Remove usage of lodash compose

* Rename get remote actions to fetch

* Include close button for savedPost modal

* fix tablet view for SavePosts and use lottie loading indicator

* Render post with content for save posts and recent mentions

* post list viewable items type definition

* Add layout width to post content for saved post screen

* Use PostWithChannel and viewableItems for saved posts and recent mentions

* Layout margin of 20

* openGraphImage margin

* Fix openGraphImage display

Co-authored-by: Elias Nahum <nahumhbl@gmail.com>

assets/base/i18n/en.json

@@ -284,7 +284,7 @@
   "mobile.oauth.switch_to_browser.error_title": "Sign in error",
   "mobile.oauth.switch_to_browser.title": "Redirecting...",
   "mobile.oauth.try_again": "Try again",
-  "mobile.open_gm.error": "",
+  "mobile.open_gm.error": "We couldn't open a group message with those users. Please check your connection and try again.",
   "mobile.permission_denied_dismiss": "Don't Allow",
   "mobile.permission_denied_retry": "Settings",
   "mobile.post_info.add_reaction": "Add Reaction",
@@ -328,6 +328,7 @@
   "mobile.routes.custom_status": "Set a Status",
   "mobile.routes.table": "Table",
   "mobile.routes.user_profile": "Profile",
+  "mobile.screen.saved_posts": "Saved Messages",
   "mobile.screen.your_profile": "Your Profile",
   "mobile.server_identifier.exists": "You are already connected to this server.",
   "mobile.server_link.error.text": "The link could not be found on this server.",
@@ -415,6 +416,8 @@
   "post.options.title": "Options",
   "posts_view.newMsg": "New Messages",
   "public_link_copied": "Link copied to clipboard",
+  "saved_posts.empty.paragraph": "To save something for later, long-press on a message and choose Save from the menu. Saved messages are only visible to you.",
+  "saved_posts.empty.title": "No saved messages yet",
   "screen.mentions.subtitle": "Messages you've been mentioned in",
   "screen.mentions.title": "Recent Mentions",
   "screen.search.placeholder": "Search messages & files",