Response type of fetchAs https://github.com/fable-compiler/fable-powerpack/blob/master/src/Fetch.fs#L359
Response type of put https://github.com/fable-compiler/fable-powerpack/blob/master/src/Fetch.fs#L401
Wanneer ik een Msg as Success wil toevoegen:
Cmd.ofPromise
(Fable.PowerPack.Fetch.putRecord "geplande-diensten" req)