chore: import upstream snapshot with attribution

Sources/ContainerPersistence/ConfigCodingStrategy.swift

@@ -0,0 +1,70 @@
+//===----------------------------------------------------------------------===//
+// Copyright © 2026 Apple Inc. and the container project authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//===----------------------------------------------------------------------===//
+
+import Foundation
+
+/// A type that provides custom decoding logic for a specific `Decodable` type
+/// when using `ConfigSnapshotDecoder`. This enables modification of `Decodable` behavior
+/// for types that already conform to `Decodable`, such as `URL` and `Measurement`.
+public protocol ConfigDecodingStrategy: Sendable {
+    associatedtype Value: Decodable
+    func decode(from decoder: Decoder) throws -> Value
+}
+
+/// A type that provides custom encoding logic for a specific `Encodable` type.
+/// This enables modification of `Encodable` behavior for types that already conform
+// to `Encodable`, such as `URL` and `Measurement`.
+public protocol ConfigEncodingStrategy: Sendable {
+    associatedtype Value: Encodable
+    func encode(_ value: Value, to encoder: Encoder) throws
+}
+
+/// A type that provides both custom encoding and decoding for the same type. Similar to `Codable`
+public typealias ConfigCodingStrategy = ConfigDecodingStrategy & ConfigEncodingStrategy
+
+/// Decodes a `URL` from a string value. e.g. "https://www.apple.com"
+public struct URLConfigDecodingStrategy: ConfigDecodingStrategy {
+    public init() {}
+
+    public func decode(from decoder: Decoder) throws -> URL {
+        let container = try decoder.singleValueContainer()
+        let string = try container.decode(String.self)
+        guard let url = URL(string: string) else {
+            throw DecodingError.dataCorrupted(
+                DecodingError.Context(
+                    codingPath: decoder.codingPath,
+                    debugDescription: "Invalid URL string: \"\(string)\"."
+                )
+            )
+        }
+        return url
+    }
+}
+
+// A type erased version of `ConfigDecodingStrategy`
+struct AnyConfigDecodingStrategy: Sendable {
+    let valueTypeID: ObjectIdentifier
+    private let decode: @Sendable (Decoder) throws -> Any
+
+    init<S: ConfigDecodingStrategy>(_ strategy: S) {
+        self.valueTypeID = ObjectIdentifier(S.Value.self)
+        self.decode = { decoder in try strategy.decode(from: decoder) as Any }
+    }
+
+    func decode(from decoder: Decoder) throws -> Any {
+        try decode(decoder)
+    }
+}