Add protocol support for AWS JSON-RPC

[jonathan343]

Note

This PR is in rough condition and I will try improving and simplifying it, but opening this so others can start viewing it.

Overview

This PR adds end-to-end awsJson1_0/awsJson1_1 support: new protocol generators and protocol-test projections, plus smithy-aws-core runtime client protocols with awsJson-specific error identification/discriminator parsing, host-prefix handling, and event-stream support. It also includes supporting infrastructure changes: improved generated protocol test assertions/SigV4 test config, shared HTTP endpoint host-prefix merging, and smithy-json non-finite numeric serde (NaN/Infinity) round-trip support.

Testing

I was able to generate a client for Amazon SQS from its smithy service model and make successfully calls:

SQS Test Script

import asyncio

from smithy_aws_core.identity import EnvironmentCredentialsResolver
from aws_sdk_sqs.client import SQSClient, ListQueuesInput
from aws_sdk_sqs.config import Config

async def main():
    client = SQSClient(
        config=Config(
            endpoint_uri="https://sqs.us-west-2.amazonaws.com",
            region="us-west-2",
            aws_credentials_identity_resolver=EnvironmentCredentialsResolver(),
        )
    )
    response = await client.list_queues(
        ListQueuesInput()
    )
    print(response)

asyncio.run(main())

Output:

(smithy-python) $ python test.py
/Users/gytndd/dev/GitHub/smithy-python/packages/aws-sdk-signers/src/aws_sdk_signers/signers.py:794: AWSSDKWarning: Payload signing is enabled. This may result in decreased performance for large request bodies.
  warnings.warn(
Unclosed client session
client_session: <aiohttp.client.ClientSession object at 0x10b598110>
ListQueuesOutput(queue_urls=['https://sqs.us-west-2.amazonaws.com/<REDACTED>.fifo', 'https://sqs.us-west-2.amazonaws.com/<REDACTED>.fifo'], next_token=None)

Next Steps

• Test with a service/operation that uses event streaming

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[JordonPhillips]

I'm not a fan of this. When you do a plain assert with two dataclasses, pytest will give you a nice result showing you the diff if they're not equal. This will fail at the first non-equal value. Also, since it only recurses on dataclasses it'll never find nan in a list or map.

In the spirit of moving things out of Java, it might be best to have a test-utils package that implements an assert that builds up an error. It could go in test dependencies so normal installs don't catch it.