Feature/ Alternative PubSub Methods

[nalchevanidze]

there should be 3 kind of resolvers:

• Query: without stream, parallel fields resolving
• Mutation: with stream , sequence fields resolving
• Subscription: with stream, parallel fields resolving, root resolver has fields with
  {
  stream:[x]
  value:: args -> ( event -> m result )
  }

would be great if we had some kind of Monad:

GQLMonad (o :: OperationKind) (m :: * -> *) event a = ...

that could change behaviour according to OperationKind

data GQLMonad (o::OperationKind) (m :: * -> * ) value where 
    QueryM :: m value -> GQLMonad 'Query m  ()
    MutationM :: Event channel event -> m value -> GQLMonad 'Mutation m (Event channel event)
    SubscriptionM ::  channel -> m (Event channel event -> m value) -> GQLMonad 'Subscription m (Event channel event)