Fix serialization
I tested it with the following code.
import Network.HTTP.Client (newManager, defaultManagerSettings)
import Network.HTTP.Client.TLS (tlsManagerSettings)
import Servant.Client (BaseUrl(BaseUrl), Scheme(Https), ClientM, client, mkClientEnv, runClientM, ClientEnv)
import Servant.API (NoContent)
import Data.Proxy (Proxy(Proxy))
import Caldera.Clients.Gecko.API (getHistory)
manager' <- newManager tlsManagerSettings
let manager'' = (mkClientEnv manager' (BaseUrl Https "api.coingecko.com" 443 ""))
let runCoinGecko = flip runClientM manager''
runCoinGecko $ getHistory "tezos" "25-11-2020"