.cargo-deny-config.toml

RPC v2 CBOR is a new protocol that ~is being added~ has [recently been
added](https://smithy.io/2.0/additional-specs/protocols/smithy-rpc-v2.html)
to the Smithy
specification.

_(I'll add more details here as the patchset evolves)_

Credit goes to @jjant for initial implementation of the router, which I
built on top of from his
[`jjant/smithy-rpc-v2-exploration`](https://github.com/awslabs/smithy-rs/tree/jjant/smithy-rpc-v2-exploration)
branch.

Tracking issue: https://github.com/smithy-lang/smithy-rs/issues/3573.

## Caveats

`TODO`s are currently exhaustively sprinkled throughout the patch
documenting what remains to be done. Most of these need to be addressed
before this can be merged in; some can be punted on to not make this PR
bigger.

However, I'd like to call out the major caveats and blockers here. I'll
keep updating this list as the patchset evolves.

- [x] RPC v2 has still not been added to the Smithy specification. It is
currently being worked on over in the
[`smithy-rpc-v2`](https://github.com/awslabs/smithy/tree/smithy-rpc-v2)
branch. The following are prerrequisites for this PR to be merged;
**until they are done CI on this PR will fail**:
    - [x] Smithy merges in RPC v2 support.
    - [x] Smithy releases a new version incorporating RPC v2 support.
- Released in [Smithy
v1.47](https://github.com/smithy-lang/smithy/releases/tag/1.47.0)
    - [x] smithy-rs updates to the new version.
        - Updated in https://github.com/smithy-lang/smithy-rs/pull/3552
- [x] ~Protocol tests for the protocol do not currently exist in Smithy.
Until those get written~, this PR resorts to Rust unit tests and
integration tests that use `serde` to round-trip messages and compare
`serde`'s encoders and decoders with ours for correctness.
- Protocol tests are under the
[`smithy-protocol-tests`](https://github.com/smithy-lang/smithy/tree/main/smithy-protocol-tests/model/rpcv2Cbor)
directory in Smithy.
- We're keeping the `serde_cbor` round-trip tests for defense in depth.
- [ ] https://github.com/smithy-lang/smithy-rs/issues/3709 - Currently
only server-side support has been implemented, because that's what I'm
most familiar. However, we're almost all the way there to add
client-side support.
- ~[ ] [Smithy `document`
shapes](https://smithy.io/2.0/spec/simple-types.html#document) are not
supported. RPC v2's specification currently doesn't indicate how to
implement them.~
- [The
spec](https://smithy.io/2.0/additional-specs/protocols/smithy-rpc-v2.html#shape-serialization)
ended up leaving them as unsupported: "Document types are not currently
supported in this protocol."

## Prerequisite PRs

This section lists prerequisite PRs and issues that would make the diff
for this one lighter or easier to understand. It's preferable that these
PRs be merged prior to this one; some are hard prerequisites. They
mostly relate to parts of the codebase I've had to touch or ~pilfer~
inspect in this PR where I've made necessary changes, refactors and
"drive-by improvements" that are mostly unrelated, although some
directly unlock things I've needed in this patchset. It makes sense to
pull them out to ease reviewability and make this patch more
semantically self-contained.

- https://github.com/awslabs/smithy-rs/pull/2516
- https://github.com/awslabs/smithy-rs/pull/2517
- https://github.com/awslabs/smithy-rs/pull/2522
- https://github.com/awslabs/smithy-rs/pull/2524
- https://github.com/awslabs/smithy-rs/pull/2528
- https://github.com/awslabs/smithy-rs/pull/2536
- https://github.com/awslabs/smithy-rs/pull/2537
- https://github.com/awslabs/smithy-rs/pull/2531
- https://github.com/awslabs/smithy-rs/pull/2538
- https://github.com/awslabs/smithy-rs/pull/2539
- https://github.com/awslabs/smithy-rs/pull/2542
- https://github.com/smithy-lang/smithy-rs/pull/3684
- https://github.com/smithy-lang/smithy-rs/pull/3678
- https://github.com/smithy-lang/smithy-rs/pull/3690
- https://github.com/smithy-lang/smithy-rs/pull/3713
- https://github.com/smithy-lang/smithy-rs/pull/3726
- https://github.com/smithy-lang/smithy-rs/pull/3752

## Testing
<!--- Please describe in detail how you tested your changes -->
<!--- Include details of your testing environment, and the tests you ran
to -->
<!--- see how your change affects other areas of the code, etc. -->

~RPC v2 has still not been added to the Smithy specification. It is
currently being worked on over in the
[`smithy-rpc-v2`](https://github.com/awslabs/smithy/tree/smithy-rpc-v2)
branch.~

This can only be tested _locally_ following these steps:

~1. Clone [the Smithy
repository](https://github.com/smithy-lang/smithy/tree/smithy-rpc-v2)
and checkout the `smithy-rpc-v2` branch.
2. Inside your local checkout of smithy-rs pointing to this PR's branch,
make sure you've added `mavenLocal()` as a repository in the
`build.gradle.kts` files.
[Example](https://github.com/smithy-lang/smithy-rs/pull/2544/commits/8df82fd3fc92434ea4f4ffb10b02df2da458624c).
4. Inside your local checkout of Smithy's `smithy-rpc-v2` branch:
1. Set `VERSION` to the current Smithy version used in smithy-rs (1.28.1
as of writing, but [check
here](https://github.com/awslabs/smithy-rs/blob/main/gradle.properties#L21)).
    2. Run `./gradlew clean build pTML`.~
~6.~ 1. In your local checkout of the smithy-rs's `smithy-rpc-v2`
branch, run `./gradlew codegen-server-test:build -P
modules='rpcv2Cbor'`.

~You can troubleshoot whether you have Smithy correctly set up locally
by inspecting
`~/.m2/repository/software/amazon/smithy/smithy-protocols-traits`.~

## Checklist
<!--- If a checkbox below is not applicable, then please DELETE it
rather than leaving it unchecked -->
- [ ] I have updated `CHANGELOG.next.toml` if I made changes to the
smithy-rs codegen or runtime crates

----

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