Event definitions for AppSync Events

There are currently no event definitions for the relatively new AWS AppSync Event service. Going through the [AWS docs](https://docs.aws.amazon.com/appsync/latest/eventapi/event-api-welcome.html), I've collected the following list of events that could be added:

1. ~~[onPublish](https://docs.aws.amazon.com/appsync/latest/eventapi/channel-namespace-handlers.html#event-handler-onpublish)~~
2. ~~[onSubscribe](https://docs.aws.amazon.com/appsync/latest/eventapi/channel-namespace-handlers.html#event-handler-onpublish)~~
3. [Lambda authorization ](https://docs.aws.amazon.com/appsync/latest/eventapi/configure-event-api-auth.html#aws-lambda-authorization), consisting of a `authorizationRequest`, `authorizationContext` and a `authorizationReponse`.
4. Optionally/debatable definitions for the [event API websocket protocol messages](https://docs.aws.amazon.com/appsync/latest/eventapi/event-api-websocket-protocol.html#realtime-websocket-operations).

I'm open to adding these myself, since I'm currently developing a system that will use AppSync Event, so I need to write them regardless.

Should these definitions live in `aws_lambda_events::events::appsync` (potentially in a sub-module) or in a new module `aws_lambda_events::events::appsync_events` ?

Edit: I've just realized that `onPublish` and `onSubscribe` only supports javascript handlers - so scratch that...

Lisez la documentation AWS AppSync Events liée dans l’issue, puis examinez le module existant aws_lambda_events::events::appsync afin de comparer son organisation avec les définitions demandées. Déterminez si l’autorisation Lambda et les messages du protocole websocket sont dans le périmètre, et s’ils doivent appartenir à appsync ou à un sous-module. La tâche est terminée lorsque les définitions AppSync Event convenues sont représentées de manière cohérente avec les modules d’événements existants.

Rédigé par le modèle d'indexation à partir du texte de l'issue.