Update cookie generation to match base64 encoding
Update cookie generation to match base64 encoding

Current code is using URLEncoding but example was using the
standard RFC 4648 encoding. Switch to using the URL
encoding in the example as well.
18F/oauth2_proxy,jehiah/oauth2_proxy,bitly/oauth2_proxy,bitly/google_auth_proxy,kalibrr/oauth2_proxy,bitly/oauth2_proxy,ploxiln/oauth2_proxy,ploxiln/oauth2_proxy,Shopify/google_auth_proxy,kalibrr/oauth2_proxy,18F/oauth2_proxy,bitly/google_auth_proxy,Shopify/google_auth_proxy,jehiah/oauth2_proxy,Shopify/google_auth_proxy