Return multiple notifications for a service.
Choosing a page_size or a page_number is no longer allowed.
Instead, there is a `next` link included with will return the
next {default_page_size} notifications in the sequence.
Query parameters accepted are:
- template_type: filter by specific template types
- status: filter by specific statuses
- older_than: return a chronological list of notifications older
than this one. The notification with the id that is passed in
is _not_ returned.
Note that both `template_type` and `status` can accept multiple
parameters. Thus it is possible to call
`/v2/notifications?status=created&status=sending&status=delivered`
The new 'v2' API wants to return less data than the previous one,
which was sending back tons of fields the clients never used.
This new route returns only useful information, with the JSON
response dict being built up in the model's `.serialize()` method.
Note that writing the test for this was a bit painful because of
having to treat loads of keys differently. Hopefully we think this
is a good way to write this test, because if we don't, we should
start thinking of a better way to check the values are what we
expect.
Start building up the validators required for post notificaiton.
The app/v2/errors.py is a rough sketch, will be passed a code, the error can look up the message and link for the error message.
