volterra_origin_pool used in route cannot be deleted as it is in use

[michaelbuemi]

Same issue as #248 except with origin pools referenced in routes.

If you try to simultaneously delete an origin pool and dereference it from a route it was in, the provider cannot figure out the dependency.

[eissko]

I can confirm we had the same issue. as workaround we had to re-design our deployment where origin pools are created ahead of the module with route. if we need to destroy origin pool, first all routes must be removed. :(