Question: Dependent return types of routes

Is it possible to do something like this?

```haskell
type API b = "other-stuff" :> Capture "bool" (SBool b) :> Get '[PlainText] (IntOrString b)

type familty IntOrString (b :: Bool) :: Type where
IntOrString 'False = Int
IntOrString 'True = String

thing :: Server (API b)
thing b =
case b of
SFalse -> pure 5
STrue -> pure "lol"
```
where `SBool` and friends are the traditional singletonised `Bool`

I originally tried to do
```haskell
type API = "other-stuff" :> forall b. Capture "bool" (SBool b) :> Get '[PlainText] (IntOrString b)
```
but `ghc` yelled at me for impredicative types. Maybe this could be worked around by making a `newtype` and instantiating some `servant` type families (?), but I'm not sure where I should be looking, and even if it works, it seems like I would need different newtypes for every endpoint :/

Context:
I have two types of things, and their types contain different data, but all queries on them are very similar (I can easily express it with type/data families).

No repository files or tests are named. Start by examining the Servant API and Server types involved in the shown singleton Bool and type-family definitions, then verify whether the dependent return type can be represented without impredicative types; done means establishing a supported approach or documenting why it is not feasible.

Written by the indexing model from the issue text.