add send_notification file for handling sending one off messages

currently, they're made by creating a one-line job, but we want to
reduce task/csv file noise so we're moving them to persist in the
same vein as API usage. However, we can't just call through to that
since there are some differences:

* no api keys
* tighter control over API format
* no scheduling
* no client references

etc.

So, re-using as much of the v2 validation stuff as possible, I've
created this file that just does basic validation, and then calls
through to persist_notification and schedules a task. Woo.

app/service/rest.py

@@ -61,6 +61,7 @@ from app.service import statistics
 from app.service.service_inbound_api_schema import service_inbound_api, update_service_inbound_api_schema
 from app.service.utils import get_whitelist_objects
 from app.service.sender import send_notification_to_service_users
+from app.service.send_notification import send_one_off_notification
 from app.schemas import (
     service_schema,
     api_key_schema,
@@ -591,3 +592,9 @@ def handle_sql_errror(e):
         return jsonify(result='error', message="No result found"), 404
     else:
         raise e
+
+
+@service_blueprint.route('/<uuid:service_id>/send-notification', methods=['POST'])
+def post_notification(service_id):
+    resp = send_one_off_notification(service_id, request.get_json())
+    return jsonify(resp), 201

app/service/send_notification.py

@@ -0,0 +1,61 @@
+from app.config import QueueNames
+from app.notifications.validators import (
+    check_service_over_daily_message_limit,
+    check_sms_content_char_count,
+    validate_and_format_recipient,
+)
+from app.notifications.process_notifications import (
+    create_content_for_notification,
+    persist_notification,
+    send_notification_to_queue,
+)
+from app.models import (
+    KEY_TYPE_NORMAL,
+    PRIORITY,
+    SMS_TYPE,
+)
+from app.dao.services_dao import dao_fetch_service_by_id
+from app.dao.templates_dao import dao_get_template_by_id_and_service_id
+
+
+def send_one_off_notification(service_id, post_data):
+    service = dao_fetch_service_by_id(service_id)
+    template = dao_get_template_by_id_and_service_id(
+        template_id=post_data['template_id'],
+        service_id=service_id
+    )
+
+    personalisation = post_data.get('personalisation', None)
+
+    if template.template_type == SMS_TYPE:
+        template_with_content = create_content_for_notification(template, personalisation)
+        check_sms_content_char_count(template_with_content.content_count)
+
+    check_service_over_daily_message_limit(KEY_TYPE_NORMAL, service)
+
+    validate_and_format_recipient(
+        send_to=post_data['to'],
+        key_type=KEY_TYPE_NORMAL,
+        service=service,
+        notification_type=template.template_type
+    )
+
+    notification = persist_notification(
+        template_id=template.id,
+        template_version=template.version,
+        recipient=post_data['to'],
+        service=service,
+        personalisation=personalisation,
+        notification_type=template.template_type,
+        api_key_id=None,
+        key_type=KEY_TYPE_NORMAL
+    )
+
+    queue_name = QueueNames.PRIORITY if template.process_type == PRIORITY else None
+    send_notification_to_queue(
+        notification=notification,
+        research_mode=service.research_mode,
+        queue=queue_name
+    )
+
+    return {'id': str(notification.id)}