[Feature Request]: Add support for update key in resources definition

[rnegron]

Current Behavior

Resources don't support more than 1 "write" action via the create key. This means that customers using resources have to "exit" out of resources to add support for update-relating write actions.

Desired Behavior / Feature Request

Update the ResourceSchema to support an optional update field. This could map to a {resourceName}Update key.

[om4csaba]

If there is consideration to open up the resource to handle updates, then I would suggest adding delete as well. Then the whole CRUD sequence would be supported by a resource.