Idempotency tokens should be ignored when applied to a nested shape

[ianbotsf]

Describe the bug

Given a model:

operation Foo {
    input := {
        bar: Bar
    }
}

structure Bar {
    @idempotencyToken
    dedpue: String
}

The generated serializer code incorrectly assumes that a context: ExecutionContext value is in scope when attempting to serialize the request. The problem is likely in SerializeStructGenerator.idempotencyTokenPostfix.

Instead, according to Smithy's trait documentation, we should be silently ignoring the trait whenever we encounter it applied to a member of a non-top-level, non-input shape. (This "desired behavior" seems incorrect, confirming with Smithy team.)

Expected behavior

Idempotency tokens should be ignored when applied to a nested or non-input shape

Current behavior

Codegen incorrectly generates serialization code for nested idempotency tokens, causing compilation to fail

Steps to Reproduce

See model above

Possible Solution

No response

Context

No response

Smithy-Kotlin version

1.2.18

Platform (JVM/JS/Native)

JVM

Operating system and version

(n/a)