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/time.go

@@ -0,0 +1,30 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package utils
+
+import (
+	"time"
+)
+
+func MillisFromTime(t time.Time) int64 {
+	return t.UnixNano() / int64(time.Millisecond)
+}
+
+func TimeFromMillis(millis int64) time.Time {
+	return time.Unix(0, millis*int64(time.Millisecond))
+}
+
+func StartOfDay(t time.Time) time.Time {
+	year, month, day := t.Date()
+	return time.Date(year, month, day, 0, 0, 0, 0, t.Location())
+}
+
+func EndOfDay(t time.Time) time.Time {
+	year, month, day := t.Date()
+	return time.Date(year, month, day, 23, 59, 59, 999999999, t.Location())
+}
+
+func Yesterday() time.Time {
+	return time.Now().AddDate(0, 0, -1)
+}