MM-15021: Adding new builtin system schema for Guests (#10601)

* MM-15021: Adding new builtin system schema for Guests

* Fixing tests

* Setting properly the permissions

* Adding guests to sampledata

* Restrict more roles updates in the app layer for guests

* Adding comment to explain that permissions migration must go at the end

* Setting the default guest role for custom scheme during migration

* Fixing import and export

* Creating scheme guest roles on migration

* Fixing tests

* Fixing tests

* Fixing tests

api4/channel.go

@@ -1041,7 +1041,7 @@ func updateChannelMemberSchemeRoles(c *Context, w http.ResponseWriter, r *http.R
 		return
 	}
 
-	if _, err := c.App.UpdateChannelMemberSchemeRoles(c.Params.ChannelId, c.Params.UserId, schemeRoles.SchemeUser, schemeRoles.SchemeAdmin); err != nil {
+	if _, err := c.App.UpdateChannelMemberSchemeRoles(c.Params.ChannelId, c.Params.UserId, schemeRoles.SchemeGuest, schemeRoles.SchemeUser, schemeRoles.SchemeAdmin); err != nil {
 		c.Err = err
 		return
 	}