middleware registration update

@fosdev Please take a look. Would be nice if dice_bag supports something like:
```yaml
discovery_middleware:
  include: true
  expiry: 20
```
If include is `false` just ignore expiry. I looked through dice_bag readme and didn't find anything about it.
I think these may come in as strings in template from configured.include_alps_middleware. Need to be careful about that.