Make KnownCaipNamespacedChainId generic over Namespace type parameter (#262)

This commit refactors `KnownCaipNamespacedChainId` (introduced in
[#258](#258)) into a generic type
by adding a `Namespace` type parameter. This allows the type to be
narrowed down to chain IDs with a specific namespace.

This is not a breaking change, as `Namespace` defaults to a type union
of known CAIP namespaces. The type's previous behavior is preserved when
its generic type parameter is omitted.

Author: MajorLift

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+
+- Make `KnownCaipNamespacedChainId` type generic over `Namespace` type parameter ([#262](https://github.com/MetaMask/utils/pull/262))
+
 ## [11.5.0]
 
 ### Added

src/caip-types.ts

@@ -148,8 +148,12 @@ export enum KnownCaipNamespace {
  *
  * This is a narrower, more type-safe alternative to {@link CaipChainId} for use cases
  * where the chain namespace must be one of the known standards.
+ *
+ * @template Namespace - The namespace of the CAIP-2 chain ID. Must be a known namespace specified in {@link KnownCaipNamespace}.
  */
-export type KnownCaipNamespacedChainId = `${KnownCaipNamespace}:${string}`;
+export type KnownCaipNamespacedChainId<
+  Namespace extends `${KnownCaipNamespace}` = `${KnownCaipNamespace}`,
+> = `${Namespace}:${string}`;
 
 /**
  * Check if the given value is a {@link CaipChainId}.