Add name and image properties to subscriptions

In my Microsub implementation, I have added support for two "follow" properties that are not yet defined in the proposed specification: name and photo. These properties let me present the feeds to which someone is subscribed in a more user-friendly way. Before this change, I could only see the feed URLs to which I should subscribe. This is not intuitive for most people.

To create a subscription (to "follow" a feed), one must specify:

- The URL of the resource to which one wants to subscribe.
- The channel in which the subscription should be created.

I would like to see this extended to include two new properties:

- `name`: The name of the feed to which one is subscribed.
- `photo`: A logo representative of the feed.

These two new attributes would allow richer displays of feed names.

Servers could optionally provide a name and a photo value. These could be gathered in various ways depending on the feed type to to which a user wants to subscribe. How to collect information for these properties should not be defined in the specification as they are out of scope. If a feed name is not found, a server should be asked to fall back to set the name as equal to the URL value, reducing the amount of validation a client needs to do on the front-end.

Here is how I display the feeds to which I am subscribed in a channel.


Start by reviewing the specification sections that define creating subscriptions and the existing follow properties. Define the optional name and photo fields and the URL fallback behavior, while keeping data collection out of scope. Done means the specification clearly describes these properties and their server behavior.

Written by the indexing model from the issue text.