sdk: add consent helper - closes #397

[aeneasr]

No description provided.

[aeneasr]

Instead of returning the consent response token here, we could probably return the URL instead. The former requires us to do something like this:

response, err := c.GenerateResponse(/* ... */)
http.Redirect(r,w,claims.RedirectURL + "&consent=" + response)

while the latter would allow for an easier flow:

redirectURL, err := c.GenerateResponse(/* ... */)
http.Redirect(r,w redirectURL)

To deny consent, the idea is to have:

redirectURL, err := c.DenyConsent(/* ... */)
http.Redirect(r,w redirectURL)

Currently this would be possible with:

http.Redirect(r,w,claims.RedirectURL + "&consent=deny")