Framework-level errors

[david-perez]

Smithy has various implicit “framework” errors that can be returned at any time from a service. For example, a SerializationException is returned by a server when a request cannot be parsed, or if there is a type mismatch between a member in the serialized request and the member in the Smithy model. This error so far has not been modeled or exposed in Smithy in any way, leading to server-side implementations needing to either hardcode them into their implementations (see smithy-rs smithy-lang/smithy-rs#3716) or create their own one-off models for framework level errors (see smithy-typescript).

One reason for this lack of modeling is that clients don’t need to know about every possible error a service can return. Clients implement generic error handling to account for unknown errors. However, servers must know about every possible error they can return, and any error a service tries to return that isn’t modeled is converted to an InternalFailureException.

I don't know exactly what my ask is here, but at the very least I would like Smithy to vend these framework-level errors from this repo, somewhere central, so implementations can consume them.