Combinator with fixed query param

I'm looking to write a Haskell program that depends on some API functions on [AlphaVantage](https://www.alphavantage.co/documentation/), and was thinking of trying out servant. However, the API is designed somewhat weirdly, with a single endpoint `query`, and a param `function` determining the remaining parameters to be taken in.

Is it possible to create a combinator with a fixed parameter (which I will name `QueryFixedParam`) that allows me to implement this API neatly? Such a combinator could work this way:

```haskell
type API = "query" :> QueryFixedParam "function" "TIME_SERIES_INTRADAY" :> ...
:<|> "query" :> QueryFixedParam "function" "TIME_SERIES_DAILY" :> ...
.
.
.
```

I'm very new to servant, so please let me know if there are better ways of implementing such an API. Thank you!

Start by reviewing servant's existing query-parameter combinators and the API type syntax shown in the issue. Determine whether a fixed function parameter can be represented for the AlphaVantage branches, or whether another API description is preferable. Done means the supported approach is implemented or the issue is clarified with a concrete alternative.

Written by the indexing model from the issue text.