Allow service backends to have access to the current request or user

[stsewd]

Hi, thank you for maintaining mama CAS!

Currently, service backends have access to the service only.

django-mama-cas/mama_cas/services/backends.py

Lines 66 to 88 in 22e3b23

	class SettingsBackend(object):
	def get_callbacks(self, service):
	return services.get_config(service, 'CALLBACKS')
	def get_logout_url(self, service):
	return services.get_config(service, 'LOGOUT_URL')
	def logout_allowed(self, service):
	return services.get_config(service, 'LOGOUT_ALLOW')
	def proxy_allowed(self, service):
	return services.get_config(service, 'PROXY_ALLOW')
	def proxy_callback_allowed(self, service, pgturl):
	try:
	return services.get_config(service, 'PROXY_PATTERN').match(pgturl)
	except AttributeError:
	return False
	def service_allowed(self, service):
	if not service:
	return False
	return services.is_valid(service)

It can be useful to have access to the current user to check if that user is allowed to access the given service.

Maybe the current user can be passed in the constructor or on each method call.

django-mama-cas/mama_cas/services/__init__.py

Line 16 in 22e3b23

backend = import_string(backend_path)()

django-mama-cas/mama_cas/models.py

Line 101 in 22e3b23

if not service_allowed(service):