use django's storage backend ManifestStaticFilesStorage for static files versioning

ECOM-3905

playbooks/roles/credentials/defaults/main.yml

@@ -121,7 +121,7 @@ CREDENTIALS_FILE_STORAGE_BACKEND:
   STATIC_ROOT: '{{ CREDENTIALS_STATIC_ROOT }}'
   MEDIA_URL: '{{ CREDENTIALS_MEDIA_URL }}'
   STATIC_URL: '{{ CREDENTIALS_STATIC_URL }}'
-  STATICFILES_STORAGE: 'django.contrib.staticfiles.storage.StaticFilesStorage'
+  STATICFILES_STORAGE: 'django.contrib.staticfiles.storage.ManifestStaticFilesStorage'
   DEFAULT_FILE_STORAGE: 'django.core.files.storage.FileSystemStorage'
 
 # Note: the protocol for CORS whitelist values is necessary for matching the correct origin by nginx

playbooks/roles/credentials/templates/edx/app/nginx/sites-available/credentials.j2

@@ -45,6 +45,7 @@ server {
   location ~ ^{{ CREDENTIALS_STATIC_URL }}(?P<file>.*) {
     root {{ CREDENTIALS_STATIC_ROOT }};
     add_header Access-Control-Allow-Origin $cors_header always;
+    add_header Cache-Control "max-age=31536000";
     try_files /$file =404;
   }