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/000012_create_commands.down.sql

@@ -0,0 +1,8 @@
+DROP INDEX IF EXISTS idx_commands_team_id;
+DROP INDEX IF EXISTS idx_commands_update_at;
+DROP INDEX IF EXISTS idx_commands_create_at;
+DROP INDEX IF EXISTS idx_commands_delete_at;
+
+ALTER TABLE commands DROP COLUMN IF EXISTS pluginid;
+
+DROP TABLE IF EXISTS commands;