'Add URLs for entities related with Identity Provider.
Add URLs pointing to:
- protocols tied to the Identity Provider'

@classmethod
def _add_related_links(cls, context, ref):

    ref.setdefault('links', {})
    base_path = ref['links'].get('self')
    if (base_path is None):
        base_path = '/'.join([IdentityProvider.base_url(context), ref['id']])
    for name in ['protocols']:
        ref['links'][name] = '/'.join([base_path, name])
