Mono repo -> Master (#22553)

Combines the following repositories into one:

https://github.com/mattermost/mattermost-server
https://github.com/mattermost/mattermost-webapp
https://github.com/mattermost/focalboard
https://github.com/mattermost/mattermost-plugin-playbooks

server/channels/db/migrations/postgres/000096_threads_threadteamid.up.sql

@@ -0,0 +1,5 @@
+-- Drop any existing TeamId column from 000094_threads_teamid.up.sql
+ ALTER TABLE threads DROP COLUMN IF EXISTS teamid;
+
+ALTER TABLE threads ADD COLUMN IF NOT EXISTS threadteamid VARCHAR(26);
+UPDATE threads SET threadteamid = channels.teamid FROM channels WHERE threads.threadteamid IS NULL AND channels.id = threads.channelid;