This removes some code which is duplicative and obscure (ie it’s not
very clear why we do `"a" * 73` even though there is a Very Good Reason
for doing so).
When we first built letters you could only send them via a CSV upload, initially we needed a way to send those files to dvla per job.
We since stopped using this page. So let's delete it!
A platform admin form accepts a list of references (one per line)
received from DVLA and sends them to the API to update notification
statuses.
References we get from DVLA start with `NOTIFY00\d`, which isn't
part of the reference we store in the database, so we remove them
before sending the data to the API.
The new `returned-letter` status should be treated as `delivered`
for now until we decide a way to display returned letters to users.
Currently requests to the API made from the admin app are going from
PaaS admin app to the nginx router ELB, which then routes them back
to the api app on PaaS.
This makes sense for external requests, but for requests made from
the admin app we could skip nginx and go directly to the api PaaS
host, which should reduce load on the nginx instances and
potentially reduce latency of the api requests.
API apps on PaaS are checking the X-Custom-Forwarder header (which
is set by nginx on proxy_pass requests) to only allow requests going
through the proxy.
This adds the custom header to the API client requests, so that they
can pass that header check without going through nginx.
Because we’re setting the API key and service ID after calling the
`__init__` method of the client it wasn’t doing the thing where it
splits the combined key into the two individual UUIDs. So we still need
to set them directly, individually on the client.
The Notify API client changed in version 4 to take two arguments, not
three (service ID was removed in favour of the combined API key).
This gets a bit gnarly because the API key has to be at least a certain
length so it can be substringed internally.
