consideration of addressable links

Nobody has claimed this yet.

cc @efucile @alexandreleroux

In the context of WIS discovery metadata, distribution links provide valuable means to guide users to interacting with data.

Consider advertising a WMS map link within a dataset's discovery metadata:

```json
{
"rel" : "items",
"type" : "image/png",
"title" : "OGC:WMS map of this dataset",
"href" : "https://example.org/wms/service=WMS&version=1.3.0&request=GetMap&layer={layer}&bbox={miny},{minx},{maxy},{maxx}&format={format}&crs={crs}&width={width}&height={height}",
"templated" : "true"
}
```

Can we accomplish something similar with AMQP or MQTT? That is, provide a URI which allows a user to click/subscribe (albeit in a known way). It looks like there is a convention for both [RabbitMQ](https://www.rabbitmq.com/uri-spec.html) and [MQTT](https://github.com/mqtt/mqtt.github.io/wiki/URI-Scheme), which go as far as connection, but there may be value in further specifying this like:

```json
{
"rel" : "items",
"type" : "application/json;subtype=x-wmo-wis",
"title" : "AMQPS feed of this dataset",
"href" : "amqps://anonymous@example.org/my-vhost/my-exchange/my-topic/my-subtopic"
}
```

Of course, non-trivial cases would go through other arrangements, but the above may be helpful as low barrier entry to PubSub advertising in WIS Metadata.

No source files or tests are named. Start by reviewing the WIS discovery metadata examples and the linked RabbitMQ and MQTT URI specifications; done would be a decided, documented approach for advertising addressable PubSub links.

Written by the indexing model from the issue text.