Remove TODOs that were actually done (#392)

        val serviceShapes = Walker(model).walkShapes(service)

        serviceShapes.forEach { it.accept(this) }

        codegenDecorator.extras(protocolConfig, rustCrate)

        // TODO: if we end up with a lot of these on-by-default customizations, we may want to refactor them somewhere

        rustCrate.finalize(

            settings,

            codegenDecorator.libRsCustomizations(

    override fun setShape(shape: SetShape): Symbol {

        val inner = this.toSymbol(shape.member)

        val builder = if (model.expectShape(shape.member.target).isStringShape) {

            // TODO: refactor / figure out how we want to handle prebaked symbols

            symbolBuilder(shape, RustType.HashSet(inner.rustType()))

        } else {

            // only strings get put into actual sets because floats are unhashable

 * 1. Override section and use a `when` clause to handle each section individually

 * 2. Call `registerSection { ... }` to register individual sections on demand.

 *

 * TODO: Factory for creating named-section generators from ProtocolConfig

 *

 * TODO: Enable using partials as a named section generator to allow defining insertions from inlineable Rust code:

 * ```rust

 * struct Config {

 *    /* section:ConfigStruct */

    }

    private fun implBlock() {

        // TODO: should enums also implement AsRef<str>?

        writer.rustBlock("impl $enumName") {

            writer.rustBlock("pub fn as_str(&self) -> &str") {

                writer.rustBlock("match self") {

        inputWriter.implBlock(inputShape, symbolProvider) {

            buildOperation(this, operationShape, customizations, sdkId)

            toHttpRequestImpl(this, operationShape, inputShape)

            // TODO: streaming shapes need special support

            rustBlock(

                "fn assemble(mut builder: #1T, body: #3T) -> #2T<#3T>",

                RuntimeType.HttpRequestBuilder,