Two nice PRs

[Olivier Dalang]

Hi !

Some time ago, I've submitted two nice (I think :-) ) PRs, but nothing happened since then.

#2344 changes ProviderRegistry.get_list to only return providers that are configured, which avoids throwing an exception when a provider is not configured. This is nice as it avoids having a website crash after initial setup, if provider's configuration is not loaded as a fixture (which is probably the case most of the time if you're distributing your app).

#2181 adds two new settings, ACCOUNT_SIGNUP_OPEN and ACCOUNT_NEW_ACCOUNTS_ACTIVE, which allows to easily configure signup without sublcassing allauth.account.adapter.DefaultAccountAdapter (which is a bit cumbersome for configuring those behaviour).

Is there anything more I can do to have this merged in master ?

Thanks for the great library,

Olivier