AlamofireDecodableUserModel.swift

struct User: Decodable, CustomStringConvertible {
    let username: String
    let name: String
    
    /// This is the key part
    /// If parameters and variable name differ
    /// you can specify custom key for mapping "eg. 'user_name'"

    enum CodingKeys: String, CodingKey {
        case username = "user_name"
        case name
    }
    
    var description: String {
        return "User: { username: \(username), name: \(name) }"
    }
}