send messages to multiple providers

at the moment only EE is enabled (this is set in app.config, but also,
only EE have a function defined for them so even if another provider was
enabled without changing the dict in cbc_proxy.py we won't trigger
anything). this commit just adds wrapper tasks that check what providers
are enabled, and invokes the send function for each provider.

The send function doesn't currently distinguish between providers for
now - as we only have EE set up. in the future we'll want to separate
the cbc_proxy_client into separate clients for separate providers.
Different providers have different lambda functions, and have different
requirements. For example, we know that the two different CBC software
solutions handle references to previous messages differently.

app/clients/cbc_proxy.py

@@ -2,6 +2,8 @@ import json
 
 import boto3
 
+from app.models import BroadcastProviders
+
 # The variable names in this file have specific meaning in a CAP message
 #
 # identifier is a unique field for each CAP message
@@ -67,6 +69,9 @@ class CBCProxyNoopClient:
 
 
 class CBCProxyClient:
+    provider_function_name_map = {
+        BroadcastProviders.EE: 'bt-ee-1-proxy',
+    }
 
     def init_app(self, app):
         self._lambda_client = boto3.client(
@@ -97,12 +102,21 @@ class CBCProxyClient:
         self,
         identifier,
     ):
+        """
+        canary - a specific lambda that does not connect to a provider, but just confirms the connectivity between
+        Notify and the CBC proxy AWS account
+        """
         self._invoke_lambda(function_name='canary', payload={'identifier': identifier})
 
     def send_link_test(
         self,
         identifier,
+        provider,
     ):
+        """
+        link test - open up a connection to a specific provider, and send them an xml payload with a <msgType> of
+        test.
+        """
         payload = {'message_type': 'test', 'identifier': identifier}
 
         self._invoke_lambda(function_name='bt-ee-1-proxy', payload=payload)
@@ -121,7 +135,6 @@ class CBCProxyClient:
             'sent': sent,
             'expires': expires,
         }
-
         self._invoke_lambda(function_name='bt-ee-1-proxy', payload=payload)
 
     # We have not implementated updating a broadcast