Ability to "fail to start"

Currently if your application model depends on the result of a task that can fail, you need to keep a Maybe on the model, because you have to call Node.startProgram with an instance of your model no matter what. If there was a way to explicitly not start the program, you could avoid the Maybe and fail directly in init. For example:

getSecureContext : Task Never (Maybe Crypto.SecureContext)
getSecureContext =
    -- Turn fail-able task into one that always resolves. 
    ...

init env =
    Init.await getSecureContext <| \maybeSecureContext ->
        when maybeSecureContext is
            Nothing ->
                Node.failToStart "Failed to get secure context."
            Just secureContext ->
                Node.startProgram
                    { model =
                        { secureContext = secureContext -- don't need a Maybe
                        ...

Probably will want something similar for Browser.

Start by reading the Node.startProgram entry point and compare it with the Browser startup API, since the issue suggests both need similar behavior. Determine how init currently handles a task result and define what an explicit failure path should mean; done means applications can fail during initialization without storing a Maybe in the model.