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/000050_create_channelmembers.up.sql

@@ -0,0 +1,20 @@
+CREATE TABLE IF NOT EXISTS channelmembers (
+    channelid varchar(26) NOT NULL,
+    userid varchar(26) NOT NULL,
+    roles varchar(64),
+    lastviewedat bigint,
+    msgcount bigint,
+    mentioncount bigint,
+    notifyprops varchar(2000),
+    lastupdateat bigint,
+    PRIMARY KEY (channelid, userid)
+);
+
+CREATE INDEX IF NOT EXISTS idx_channelmembers_user_id ON channelmembers(userid);
+
+ALTER TABLE channelmembers ADD COLUMN IF NOT EXISTS schemeuser boolean;
+ALTER TABLE channelmembers ADD COLUMN IF NOT EXISTS schemeadmin boolean;
+
+ALTER TABLE channelmembers ADD COLUMN IF NOT EXISTS schemeguest boolean;
+
+DROP INDEX IF EXISTS idx_channelmembers_channel_id;