feat: add remove upstream and remove upstream target handlers

apps/api/src/services/nginx/upstream.rs

@@ -208,6 +208,11 @@ impl UpstreamService {
                 )))?
         });
         with_conn!(&*self.connection, tx, conn, {
+            // delete all targets belonging to the upstream
+            upstream_target::Entity::delete_many()
+                .filter(upstream_target::Column::UpstreamId.eq(upstream_id))
+                .exec(*conn)
+                .await?;
             model.delete(*conn).await?;
             Ok(())
         })