Constrained shapes that reach @sensitive shapes don't implement Debug

[david-perez]

Minimal reproducer:

$version: "2.0"

namespace com.amazonaws.simple

use aws.protocols#restJson1
use smithy.framework#ValidationException

@restJson1
service SimpleService {
    operations: [
        Operation
    ]
}

@http(uri: "/operation", method: "POST")
operation Operation {
    input: OperationInputOutput
    output: OperationInputOutput
    errors: [ValidationException]
}

structure OperationInputOutput {
    constrainedList: ConstrainedList
}

@length(min: 69)
list ConstrainedList {
    member: SensitiveStructure
}

@sensitive
structure SensitiveStructure {
    password: String
}

Generates:

#[allow(missing_docs)] // documentation missing in model
#[derive(
    std::clone::Clone, std::cmp::Eq, std::cmp::PartialEq, std::fmt::Debug, std::hash::Hash,
)]
pub struct OperationInput {
    #[allow(missing_docs)] // documentation missing in model
    #[doc(hidden)]
    pub constrained_list: std::option::Option<crate::model::ConstrainedList>,
}

...

#[derive(std::clone::Clone, std::cmp::Eq, std::cmp::PartialEq, std::hash::Hash)]
pub struct ConstrainedList(pub(crate) std::vec::Vec<crate::model::SensitiveStructure>);

...

#[allow(missing_docs)] // documentation missing in model
#[derive(std::clone::Clone, std::cmp::Eq, std::cmp::PartialEq, std::hash::Hash)]
pub struct SensitiveStructure {
    #[allow(missing_docs)] // documentation missing in model
    #[doc(hidden)]
    pub password: std::option::Option<std::string::String>,
}

...

impl std::fmt::Debug for SensitiveStructure {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let mut formatter = f.debug_struct("SensitiveStructure");
        formatter.field("password", &"*** Sensitive Data Redacted ***");
        formatter.finish()
    }
}

And so we get:

error[E0277]: `ConstrainedList` doesn't implement `std::fmt::Debug`
 --> simple/rust-server-codegen/src/input.rs:9:5
  |
4 |     std::clone::Clone, std::cmp::Eq, std::cmp::PartialEq, std::fmt::Debug, std::hash::Hash,
  |                                                           --------------- in this derive macro expansion
...
9 |     pub constrained_list: std::option::Option<crate::model::ConstrainedList>,
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `ConstrainedList` cannot be formatted using `{:?}`

The mistake is around here:

https://github.com/awslabs/smithy-rs/blob/35f2f27a8380a1310c264a386e162cd9f2180137/codegen-server/src/main/kotlin/software/amazon/smithy/rust/codegen/server/smithy/ConstrainedShapeSymbolMetadataProvider.kt#L46-L48

Here, we're not adding #[derive(Debug)] on the constrained shape ConstrainedList because containerDefaultMetadata(shape, model).derives does not include Debug: indeed, SensitiveStructure does not #[derive(Debug)] because it implements Debug manually.