access method to null when no url

[michael-conway]

just have one suggestion for the data presented under the "access_methods" property, particularly for the access method where type == "https". Right now, under the "access_url" property, you have "access_url": {"url": "", "headers": []}

Would it be easier to have "access_url": null, or simply leave out the property altogether? The reason I mention this is that it's impossible to get any data from access_url (as the url is blank), so clients may get confused thinking they can download via the access_url, when really they have to use the access_id

The specification only requires either access_url or access_id to be included, not both. This issue currently doesn't affect my client, as the client checks first for access id before looking at access url. But other clients may get confused when they see the "access_url" property, only to find that the "url" field is blank.