Deserialize Extended S3 Errors

[rcoh]

Issue #, if available: Fixes #422
Description of changes: This adds support for deserializing host id from errors for S3.

Semi related changes:

• fix trailing whitespace that caused cargo fmt to crash
• add support for AWS-specific inline code
• fix opaque error when an inline dependency can't be found
• expose meta() on generated errors
• add integration test to S3

Example generated code:

pub fn parse_generic_error(
    response: &http::Response<bytes::Bytes>,
) -> Result<smithy_types::Error, smithy_xml::decode::XmlError> {
    let base_err = crate::rest_xml_unwrapped_errors::parse_generic_error(response.body().as_ref())?;
    Ok(crate::s3_errors::parse_extended_error(base_err, &response))
}

The advantage of this style of override is we actually only generating this change in a single place and just invoke this function when deserializing all s3 errors

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[jdisanti]

Looks good! Just some minor comments.

[jdisanti]

Minor optimization: don't convert into a builder unless you know for certain you have a host_id to add.

[rcoh]

converting into a builder will probably just get optimized, it's just a newtype that exposes setters

[jdisanti]

Add a test case for when the header is missing.

[jdisanti]

Since this is inheriting an interface, there isn't really a super. It has a default implementation, but that just returns currentProtocols. This line doesn't seem necessary.

[rcoh]

derp, you are totally right

[jdisanti]

👍