How to do some initialisation before a nested generic sub api to avoid code duplication?

Right now I have something like this:

```haskell
data MainAPI mode = MainAPI
{ subRoute :: mode :- "sub" :> Auth '[JWT] User :> NamedRoutes SubAPI
}

data SubAPI mode = SubAPI
{ subSubRoute1 :: mode :- Post [JSON] Result
, subSubRoute2 :: mode :- "omg" :> Get [JSON] Result
}
```

When implementing this I'd have to give to the `subRoute` a function of type `AuthResult User -> SubAPI ( AsServerT AppM )`. This doesn't allow me to fail the whole sub API if user was not successfully authenticated. Instead, I have to do this check on each of the individual `subSubRoute`s.

This becomes a problem if I have many deeply nested records. Then I have to duplicate a lot of initialization steps on each tree leaf, instead of just on the root node of particular branch that share this common initialization step.

For example, besides checking for `AuthResult` I might also want to initialize a `Haxl` environment that's going to be used in all of the sub APIs. This makes me think that maybe instead of `AuthResult User -> SubAPI ( AsServerT AppM )` the `NamedRoutes` combinator should expect a `AuthResult User -> AppM ( SubAPI ( AsServerT AppM ) )` instead. This would allow me to immediately invalidate this whole branch if user is not authenticated, and I can also do some shared AppM stuff that relates to all of the sub nodes.