Add authenticateWithResponse for custom responses

[stevysmith]

Added a new method to allow someone to pass in a custom response, for example:

struct AuthenticationResponse: Decodable {
    let accessToken: String

    enum CodingKeys: String, CodingKey {
        case accessToken = "access_token"
    }
}

this is implemented through:

authKit.authenticateWithResponse(path: path, email: email, password: password, responseType: AuthenticationResponse.self)

User can then define attributes they want to collect from the response and also set the token from the response:

Configuration.auth.setBearerToken(to: response.accessToken)

Added it as two methods as potentially might want to support multiple methods with responses (oAuth & basic) and not just featherweight in the future.