dao_get_all_broadcast_messages returns just fields govuk alerts need

app/v2/govuk_alerts/get_broadcasts.py

@@ -1,8 +1,10 @@
 from flask import jsonify
 
+from app.dao.broadcast_message_dao import dao_get_all_broadcast_messages
 from app.v2.govuk_alerts import v2_govuk_alerts_blueprint
 
 
 @v2_govuk_alerts_blueprint.route('')
 def get_broadcasts():
-    return jsonify({})
+    all_broadcasts = dao_get_all_broadcast_messages()
+    return jsonify(all_broadcasts)