Update oauth2_proxy settings for MyUSA

Also, keeps the _oauthproxy cookie name, which now defaults to _oauth2_proxy
in the latest release.

deploy/usr/local/18f/etc/oauth2_proxy.cfg

@@ -47,5 +47,14 @@ cookie_expire = "168h"
 cookie_refresh = "144h"
 cookie_https_only = true
 
+## To maintain backward compatibility so users won't have to refresh.
+cookie_key = "_oauthproxy"
+
+## MyUSA settings until staging.my.usa.gov change committed
+login_url = "https://staging.18f.gov/oauth/authorize"
+redeem_url = "https://staging.18f.gov/oauth/token"
+profile_url = "https://staging.18f.gov/api/v1/profile"
+validate_url = "https://staging.18f.gov/api/v1/tokeninfo"
+
 provider = "myusa"
 pass_access_token = true