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/utils/backoff.go

@@ -0,0 +1,26 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package utils
+
+import (
+	"time"
+)
+
+var backoffTimeouts = []time.Duration{50 * time.Millisecond, 100 * time.Millisecond, 200 * time.Millisecond, 200 * time.Millisecond, 400 * time.Millisecond, 400 * time.Millisecond}
+
+// ProgressiveRetry executes a BackoffOperation and waits an increasing time before retrying the operation.
+func ProgressiveRetry(operation func() error) error {
+	var err error
+
+	for attempts := 0; attempts < len(backoffTimeouts); attempts++ {
+		err = operation()
+		if err == nil {
+			return nil
+		}
+
+		time.Sleep(backoffTimeouts[attempts])
+	}
+
+	return err
+}