Simple JSON decoding using protocol and default implementation. With this you can separate the decodable logic from repository and api client

JSONDecode+JSONMapping.swift

public enum DecodeError: Swift.Error {
    case connectivity
    case invalidData
}

protocol JSONDecodable {
    static func jsonDecode<D: Decodable>(
        _ data: Data,
        from response: HTTPURLResponse
    ) throws -> D
}

extension JSONDecodable {
    static func jsonDecode<D: Decodable>(
        _ data: Data,
        from response: HTTPURLResponse
    ) throws -> D {
        guard response.isOK,
              let root = try? JSONDecoder().decode(D.self, from: data)
        else {
            throw DecodeError.invalidData
        }
        
        return root
    }
}

protocol JSONMapper: JSONDecodable {
    typealias GetResult<T> = Swift.Result<T, Error>
    
    static func map<T: Decodable>(
        _ data: Data,
        from response: HTTPURLResponse
    ) -> GetResult<T>
}

extension JSONMapper {
    static func map<T: Decodable>(
        _ data: Data,
        from response: HTTPURLResponse
    ) -> GetResult<T> {
        do {
            let items: T = try Self.jsonDecode(data, from: response)
            return .success(items)
        } catch {
            return .failure(error)
        }
    }
}