PLT-1326: Enable channel posts of type join or leave not trigger unread notifications

model/post.go

@@ -10,9 +10,10 @@ import (
 )
 
 const (
-	POST_DEFAULT          = ""
-	POST_SLACK_ATTACHMENT = "slack_attachment"
-	POST_JOIN_LEAVE       = "join_leave"
+	POST_SYSTEM_MESSAGE_PREFIX = "system_"
+	POST_DEFAULT               = ""
+	POST_SLACK_ATTACHMENT      = "slack_attachment"
+	POST_JOIN_LEAVE            = "system_join_leave"
 )
 
 type Post struct {
@@ -159,3 +160,7 @@ func (o *Post) AddProp(key string, value interface{}) {
 
 func (o *Post) PreExport() {
 }
+
+func (o *Post) IsSystemMessage() bool {
+	return len(o.Type) >= len(POST_SYSTEM_MESSAGE_PREFIX) && o.Type[:len(POST_SYSTEM_MESSAGE_PREFIX)] == POST_SYSTEM_MESSAGE_PREFIX
+}