Option to save oauth redirect parameters

[GDay]

In some cases, the oauth server returns more back to the chiefonboarding instance than just the code (which is necessary to get the actual access/refresh tokens).

If you want to save the extra GET parameters as well, then you can enable store_redirect_parameters in the oauth config.

If you enabled the store_redirect_parameters value, then you can get the parameters by doing:

{{ oauth.redirect_params.<your param name> }}

[coveralls]

coverage: 89.751% (+0.003%) from 89.748%
when pulling ae30685 on save-oauth-redirect-params
into 8920b0b on master.