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).
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.
As before the service manager will not be able to change the Text message sender once they have the inbound sms permission.
If the inbound sms permission is turned off the Text message sender setting is once more configurable by the service manager.
The inbound number remains bound to the service, but has "inactive", so that the number can not be used again.
