Remove support for Reach provider

This provider was never active and support was never completed, so
there's little value in keeping all this potentially confusing code.

app/clients/sms/reach.py

@@ -1,52 +0,0 @@
-import json
-
-from requests import RequestException, request
-
-from app.clients.sms import SmsClient, SmsClientResponseException
-
-
-def get_reach_responses(status, detailed_status_code=None):
-    if status == 'TODO-d':
-        return ("delivered", "TODO: Delivered")
-    elif status == 'TODO-tf':
-        return ("temporary-failure", "TODO: Temporary failure")
-    elif status == 'TODO-pf':
-        return ("permanent-failure", "TODO: Permanent failure")
-    else:
-        raise KeyError
-
-
-class ReachClient(SmsClient):
-    def init_app(self, *args, **kwargs):
-        super().init_app(*args, **kwargs)
-        self.url = self.current_app.config.get('REACH_URL')
-
-    @property
-    def name(self):
-        return 'reach'
-
-    def try_send_sms(self, to, content, reference, international, sender):
-        data = {
-            # TODO
-        }
-
-        try:
-            response = request(
-                "POST",
-                self.url,
-                data=json.dumps(data),
-                headers={
-                    'Content-Type': 'application/json',
-                },
-                timeout=60
-            )
-
-            response.raise_for_status()
-            try:
-                json.loads(response.text)
-            except (ValueError, AttributeError):
-                raise SmsClientResponseException("Invalid response JSON")
-        except RequestException:
-            raise SmsClientResponseException("Request failed")
-
-        return response