[feature] Ability to reference each "line" of filters in the notification (use different filter values separately in a notification)

Ability to reference each "line" of filters in the notification (use different filter values separately in a notification)

For example you have three filters

```
.one
.two
.three
```

then in the notification you could write

```
{{ filter|1 }}
{{ filter|2 }}
{{ filter|3 }}
```

or as some request like `gets://mysite.com/api/{{filter|2}}`

No files, tests, or entry points are named. Start by locating notification template rendering and the handling of multi-line filters, then determine how separate filter values should be exposed in notification and URL templates. Done means the proposed syntax works for each example and existing notifications remain compatible.

Written by the indexing model from the issue text.