Make it explicit that whitenoise is being used

As per http://whitenoise.evans.io/en/stable/django.html#enable-whitenoise,
the whitenoise middleware should be added just after the django-security
middleware.

app/app/settings.py

@@ -55,6 +55,7 @@ INSTALLED_APPS = [
 
 MIDDLEWARE = [
     'django.middleware.security.SecurityMiddleware',
+    'whitenoise.middleware.WhiteNoiseMiddleware',
     'django.contrib.sessions.middleware.SessionMiddleware',
     'django.middleware.common.CommonMiddleware',
     'django.middleware.csrf.CsrfViewMiddleware',
@@ -88,6 +89,8 @@ STATICFILES_DIRS = [
     os.path.join(BASE_DIR, 'server/static'),
 ]
 
+STATICFILES_STORAGE = 'whitenoise.storage.CompressedManifestStaticFilesStorage'
+
 WSGI_APPLICATION = 'app.wsgi.application'
 
 AUTHENTICATION_BACKENDS = [