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/mysql/000036_create_sharedchannelusers.up.sql

@@ -0,0 +1,68 @@
+CREATE TABLE IF NOT EXISTS SharedChannelUsers (
+  Id varchar(26) NOT NULL,
+  UserId varchar(26) DEFAULT NULL,
+  RemoteId varchar(26) DEFAULT NULL,
+  CreateAt bigint(20) DEFAULT NULL,
+  LastSyncAt bigint(20) DEFAULT NULL,
+  PRIMARY KEY (Id)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
+
+SET @preparedStatement = (SELECT IF(
+    (
+        SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS
+        WHERE table_name = 'SharedChannelUsers'
+        AND table_schema = DATABASE()
+        AND column_name = 'ChannelId'
+    ) > 0,
+    'SELECT 1',
+    'ALTER TABLE SharedChannelUsers ADD ChannelId varchar(26) DEFAULT NULL;'
+));
+
+PREPARE alterIfNotExists FROM @preparedStatement;
+EXECUTE alterIfNotExists;
+DEALLOCATE PREPARE alterIfNotExists;
+
+SET @preparedStatement = (SELECT IF(
+    (
+        SELECT COUNT(*) FROM information_schema.TABLE_CONSTRAINTS
+        WHERE table_name = 'SharedChannelUsers'
+        AND table_schema = DATABASE()
+        AND constraint_type = 'UNIQUE'
+    ) > 0,
+    'SELECT 1',
+    'ALTER TABLE SharedChannelUsers ADD CONSTRAINT UNIQUE KEY UserId(UserId, ChannelId, RemoteId)'
+));
+
+PREPARE alterIfUniqueNotExists FROM @preparedStatement;
+EXECUTE alterIfUniqueNotExists;
+DEALLOCATE PREPARE alterIfUniqueNotExists;
+
+SET @preparedStatement = (SELECT IF(
+    (
+        SELECT COUNT(*) FROM INFORMATION_SCHEMA.STATISTICS
+        WHERE table_name = 'SharedChannelUsers'
+        AND table_schema = DATABASE()
+        AND index_name = 'idx_sharedchannelusers_user_id'
+    ) > 0,
+    'DROP INDEX idx_sharedchannelusers_user_id ON SharedChannelUsers;',
+    'SELECT 1'
+));
+
+PREPARE removeIndexIfExists FROM @preparedStatement;
+EXECUTE removeIndexIfExists;
+DEALLOCATE PREPARE removeIndexIfExists;
+
+SET @preparedStatement = (SELECT IF(
+    (
+        SELECT COUNT(*) FROM INFORMATION_SCHEMA.STATISTICS
+        WHERE table_name = 'SharedChannelUsers'
+        AND table_schema = DATABASE()
+        AND index_name = 'idx_sharedchannelusers_remote_id'
+    ) > 0,
+    'SELECT 1',
+    'CREATE INDEX idx_sharedchannelusers_remote_id ON SharedChannelUsers(RemoteId);'
+));
+
+PREPARE createIndexIfNotExists FROM @preparedStatement;
+EXECUTE createIndexIfNotExists;
+DEALLOCATE PREPARE createIndexIfNotExists;