[MM-42068] Add check to stop custom groups linking to teams and channels (#19633)

* tools updates

* Revert "tools updates"

This reverts commit 6293297b55803c5a263e200ebd80192899666ae9.

* stop custom groups linking to teams and channels

* updating test and changing logic

Co-authored-by: Benjamin Cooke <benjamincooke@Benjamins-MacBook-Pro.local>
Co-authored-by: Benjamin Cooke <benjamincooke@Benjamins-MBP.ht.home>

api4/group.go

@@ -297,6 +297,17 @@ func linkGroupSyncable(c *Context, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	group, groupErr := c.App.GetGroup(c.Params.GroupId, nil)
+	if groupErr != nil {
+		c.Err = groupErr
+		return
+	}
+
+	if group.Source != model.GroupSourceLdap {
+		c.Err = model.NewAppError("Api4.linkGroupSyncable", "app.group.crud_permission", nil, "", http.StatusBadRequest)
+		return
+	}
+
 	auditRec := c.MakeAuditRecord("linkGroupSyncable", audit.Fail)
 	defer c.LogAuditRec(auditRec)
 	auditRec.AddMeta("group_id", c.Params.GroupId)