Wrap id types for type safety

[ThomasWeiser]

Instead of

type alias Proposal =
    { id : String
    , ...
    }

we should use

type alias Proposal =
    { id : ProposalId
    , ...
    }
type ProposalId = ProposalId String

Same goes for ParticipantId and AccessToken.

This way we strengthen type safety and get better self-documenting code when passing this values around.

[ThomasWeiser]

Will have to check if it's worthwhile or too much boilerplate.
Deferred for now.

[ThomasWeiser]

Recently Richard Feldman wrote that union types may get comparable sometime.

Working with wrapped types would become much easier then and we should use them for type safety.

[oliverbarnes]

Sounds good.