Architecture: Key and Value traits have circular dependency

[drmingdrmer]

Summary

The Key and Value traits have a circular dependency - each requires the other as an associated type.

Location

crates/kvapi/src/kvapi/key.rs:52-57

pub trait Key: KeyCodec + Debug {
    type ValueType: kvapi::Value;  // Key knows about Value
    // ...
}

crates/kvapi/src/kvapi/value.rs:20-21

pub trait Value: Debug {
    type KeyType: kvapi::Key;  // Value knows about Key
    // ...
}

Problem

This circular dependency:

• Makes the traits harder to understand and implement separately
• Creates unnecessary coupling between key and value abstractions
• Complicates trait bounds in generic code
• Prevents implementing one trait without the other

Impact

• More complex generic signatures throughout the codebase
• Harder to add new key or value types
• Cognitive overhead when working with the API

Suggested Fix

Consider whether Value::KeyType is truly necessary. The dependency_keys() method could potentially accept string keys instead:

pub trait Value: Debug {
    // Remove KeyType association if not strictly needed
    fn dependency_keys(&self, key: &str) -> impl IntoIterator<Item = String>;
}

Or if bidirectional navigation is needed, use a separate KeyValuePair trait that brings them together.

Priority

P2 - API design improvement