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/000020_create_posts.up.sql

@@ -0,0 +1,51 @@
+CREATE TABLE IF NOT EXISTS posts (
+    id VARCHAR(26) PRIMARY KEY,
+    createat bigint,
+    updateat bigint,
+    deleteat bigint,
+    userid VARCHAR(26),
+    channelid VARCHAR(26),
+    rootid VARCHAR(26),
+    parentid VARCHAR(26),
+    originalid VARCHAR(26),
+    message VARCHAR(65535),
+    type VARCHAR(26),
+    props VARCHAR(8000),
+    hashtags VARCHAR(1000),
+    filenames VARCHAR(4000)
+);
+
+ALTER TABLE posts ADD COLUMN IF NOT EXISTS fileids VARCHAR(300);
+ALTER TABLE posts ADD COLUMN IF NOT EXISTS hasreactions boolean;
+ALTER TABLE posts ADD COLUMN IF NOT EXISTS editat bigint;
+ALTER TABLE posts ADD COLUMN IF NOT EXISTS ispinned boolean;
+
+CREATE INDEX IF NOT EXISTS idx_posts_update_at ON posts(updateat);
+CREATE INDEX IF NOT EXISTS idx_posts_create_at ON posts(createat);
+CREATE INDEX IF NOT EXISTS idx_posts_delete_at ON posts(deleteat);
+CREATE INDEX IF NOT EXISTS idx_posts_root_id ON posts(rootid);
+CREATE INDEX IF NOT EXISTS idx_posts_user_id ON posts(userid);
+CREATE INDEX IF NOT EXISTS idx_posts_is_pinned ON posts(ispinned);
+CREATE INDEX IF NOT EXISTS idx_posts_channel_id_update_at ON posts(channelid, updateat);
+CREATE INDEX IF NOT EXISTS idx_posts_channel_id_delete_at_create_at ON posts(channelid, deleteat, createat);
+CREATE INDEX IF NOT EXISTS idx_posts_message_txt ON posts USING gin(to_tsvector('english', message));
+CREATE INDEX IF NOT EXISTS idx_posts_hashtags_txt ON posts USING gin(to_tsvector('english', hashtags));
+
+ALTER TABLE posts ADD COLUMN IF NOT EXISTS remoteid VARCHAR(26);
+
+DROP INDEX IF EXISTS idx_posts_channel_id;
+
+DO $$
+DECLARE 
+    column_exist boolean := false;
+BEGIN
+SELECT count(*) != 0 INTO column_exist
+    FROM information_schema.columns
+    WHERE table_name = 'posts'
+    AND table_schema = current_schema()
+    AND column_name = 'fileids'
+    AND NOT data_type = 'varchar(300)';
+IF column_exist THEN
+    ALTER TABLE posts ALTER COLUMN fileids TYPE varchar(300);
+END IF;
+END $$;