PLT-8522 Added separate messages for being removed from channel or team (#8078)

model/post.go

@@ -24,8 +24,9 @@ const (
 	POST_LEAVE_TEAM            = "system_leave_team"
 	POST_ADD_REMOVE            = "system_add_remove" // Deprecated, use POST_ADD_TO_CHANNEL or POST_REMOVE_FROM_CHANNEL instead
 	POST_ADD_TO_CHANNEL        = "system_add_to_channel"
-	POST_ADD_TO_TEAM           = "system_add_to_team"
 	POST_REMOVE_FROM_CHANNEL   = "system_remove_from_channel"
+	POST_ADD_TO_TEAM           = "system_add_to_team"
+	POST_REMOVE_FROM_TEAM      = "system_remove_from_team"
 	POST_HEADER_CHANGE         = "system_header_change"
 	POST_DISPLAYNAME_CHANGE    = "system_displayname_change"
 	POST_PURPOSE_CHANGE        = "system_purpose_change"
@@ -177,11 +178,12 @@ func (o *Post) IsValid() *AppError {
 		POST_ADD_REMOVE,
 		POST_JOIN_CHANNEL,
 		POST_LEAVE_CHANNEL,
-		POST_LEAVE_TEAM,
-		POST_REMOVE_FROM_CHANNEL,
-		POST_ADD_TO_CHANNEL,
-		POST_ADD_TO_TEAM,
 		POST_JOIN_TEAM,
+		POST_LEAVE_TEAM,
+		POST_ADD_TO_CHANNEL,
+		POST_REMOVE_FROM_CHANNEL,
+		POST_ADD_TO_TEAM,
+		POST_REMOVE_FROM_TEAM,
 		POST_SLACK_ATTACHMENT,
 		POST_HEADER_CHANGE,
 		POST_PURPOSE_CHANGE,