v0.4.4

Note: This release contains an important security fix.

• [PowAssent.Plug] Now uses String.to_existing_atom/1 in PowAssent.Plug.providers_for_current_user/1
• [PowAssent.Plug] Fixed security issue by removing String.to_atom/1 for user provided binary in PowAssent.Plug.authorize_url/3 and PowAssent.Plug.callback/4
• [PowAssent.Config] PowAssent.Config.get_provider_config/2 now accepts binary provider