TwitterOAuthAuthorizationHeader.swift

private func oAuthAuthorizationHeader(parameters: [URLQueryItem]) -> String {
    var parameterComponents: [String] = []
    for parameter in parameters {
        let name = parameter.name.oAuthURLEncodedString
        let value = parameter.value?.oAuthURLEncodedString ?? ""
        parameterComponents.append("\(name)=\"\(value)\"")
    }
    return "OAuth " + parameterComponents.sorted().joined(separator: ", ")
}