Fix Organization delete when groups are configured

With existing groups configured within an org, deleting that org would
fail because of Foreign Key issues.

This PR fixes this by making sure the groups get deleted before the org does.

Fixes #3247

src/db/models/group.rs

@@ -151,6 +151,13 @@ impl Group {
         }
     }
 
+    pub async fn delete_all_by_organization(org_uuid: &str, conn: &mut DbConn) -> EmptyResult {
+        for group in Self::find_by_organization(org_uuid, conn).await {
+            group.delete(conn).await?;
+        }
+        Ok(())
+    }
+
     pub async fn find_by_organization(organizations_uuid: &str, conn: &mut DbConn) -> Vec<Self> {
         db_run! { conn: {
             groups::table