Add metric warning support (announcement bar and DM) (#14483)

* Admin. Advisory: Add warning for number of active users metric status

Co-authored-by: Catalin Tomai <catalin.tomai@mattermost.com>

model/bot.go

@@ -13,9 +13,10 @@ import (
 )
 
 const (
-	BOT_DISPLAY_NAME_MAX_RUNES = USER_FIRST_NAME_MAX_RUNES
-	BOT_DESCRIPTION_MAX_RUNES  = 1024
-	BOT_CREATOR_ID_MAX_RUNES   = KEY_VALUE_PLUGIN_ID_MAX_RUNES // UserId or PluginId
+	BOT_DISPLAY_NAME_MAX_RUNES   = USER_FIRST_NAME_MAX_RUNES
+	BOT_DESCRIPTION_MAX_RUNES    = 1024
+	BOT_CREATOR_ID_MAX_RUNES     = KEY_VALUE_PLUGIN_ID_MAX_RUNES // UserId or PluginId
+	BOT_WARN_METRIC_BOT_USERNAME = "mattermost-advisor"
 )
 
 // Bot is a special type of User meant for programmatic interactions.