Update model and controller to handle parent_folder_id when creating a template.

If the parent_folder_id then check if the folder exists and is for the same service. If it is add the folder to the template model object, the relationship will be persisted when the template is saved. If the folder does not exist or is for a different service, then return a ResultNotFound error.

tests/app/template/test_rest.py

@@ -2,6 +2,7 @@ import base64
 import json
 import random
 import string
+import uuid
 from datetime import datetime, timedelta
 
 import botocore
@@ -12,7 +13,13 @@ from freezegun import freeze_time
 from notifications_utils import SMS_CHAR_COUNT_LIMIT
 
 
-from app.models import Template, SMS_TYPE, EMAIL_TYPE, LETTER_TYPE, TemplateHistory, TemplateFolder
+from app.models import (
+    EMAIL_TYPE,
+    LETTER_TYPE,
+    SMS_TYPE,
+    Template,
+    TemplateHistory
+)
 from app.dao.templates_dao import dao_get_template_by_id, dao_redact_template
 
 from tests import create_authorization_header
@@ -125,6 +132,28 @@ def test_create_template_should_return_404_if_folder_is_for_a_different_service(
     assert response.status_code == 404
 
 
+def test_create_template_should_return_404_if_folder_does_not_exist(
+        client, sample_service
+):
+    data = {
+        'name': 'my template',
+        'template_type': 'sms',
+        'content': 'template <b>content</b>',
+        'service': str(sample_service.id),
+        'created_by': str(sample_service.users[0].id),
+        'parent_folder_id': str(uuid.uuid4())
+    }
+    data = json.dumps(data)
+    auth_header = create_authorization_header()
+
+    response = client.post(
+        '/service/{}/template'.format(sample_service.id),
+        headers=[('Content-Type', 'application/json'), auth_header],
+        data=data
+    )
+    assert response.status_code == 404
+
+
 def test_should_raise_error_if_service_does_not_exist_on_create(client, sample_user, fake_uuid):
     data = {
         'name': 'my template',