Event Source Subscriptions

The limitation of subscriptions being tied to mutations is mind boggling to me - I would say the vast majority of meaningful applications are not simple crud behind a graphql api, and that's what AppSync's subscriptions are currently designed for.

I propose generic event sources for subscriptions instead of tying them to mutations. An EventBridge event bus is the most obvious event source as a starting place.

Have a subscription lambda resolver that is triggered with the event bridge event and the subscription arguments as inputs on every event. That resolver does whatever is necessary to return the data shape specified in the schema.

Start by reviewing the AWS AppSync subscription model and the EventBridge event flow described in the issue. Clarify the subscription Lambda resolver inputs and expected schema-shaped output, then define the design and acceptance criteria for generic event sources.

Written by the indexing model from the issue text.