Add auth plugin options to options list

Currently the oslo.config.opts entry_points provided by oslo.limit
doesn't include options for auth plugins, thus the parameters to
define credentials like username, password and etc are not picked up by
oslo-config-generator.

This adds the options for auth plugin options to the entry point so
that the auth parameters are included by the generated config files
and users can easily find the parameters to define the required user
credential.

Note that keystoneauth provides several plugins but this change covers
only password plugins, assuming the password authentication is most
popularly used.

Change-Id: Ib440f58b589076677be9e90dd960cd4459e63746

oslo_limit/opts.py

@@ -44,6 +44,9 @@ def list_opts():
     return [(_option_group,
              copy.deepcopy(_options) +
              loading.get_session_conf_options() +
+             loading.get_auth_plugin_conf_options('password'),
+             loading.get_auth_plugin_conf_options('v2password'),
+             loading.get_auth_plugin_conf_options('v3password'),
              loading.get_adapter_conf_options(include_deprecated=False)
              )]