Allow custom domain to be used with public S3 bucket

This allows a S3 bucket to be put behind CloudFront which
is considered best practice.

Author: cjh1

src/settings/base.py

@@ -386,6 +386,7 @@ def setup_celery_logging(**kwargs):
                 "use_ssl": os.environ.get('S3_USE_SIGV4', 'true').lower() == 'true',
                 "querystring_auth": os.environ.get('AWS_QUERYSTRING_AUTH'),
                 "default_acl": os.environ.get('AWS_DEFAULT_ACL'),
+                "custom_domain": os.environ.get("AWS_S3_PUBLIC_CUSTOM_DOMAIN", ""),
             },
         },
         "bundle": {
@@ -473,6 +474,7 @@ def setup_celery_logging(**kwargs):
 AWS_STORAGE_PRIVATE_BUCKET_NAME = os.environ.get('AWS_STORAGE_PRIVATE_BUCKET_NAME')
 AWS_S3_CALLING_FORMAT = os.environ.get('AWS_S3_CALLING_FORMAT', 'boto.s3.connection.OrdinaryCallingFormat')
 AWS_S3_ENDPOINT_URL = os.environ.get('AWS_S3_ENDPOINT_URL', '')
+AWS_S3_PUBLIC_CUSTOM_DOMAIN = os.environ.get('AWS_S3_PUBLIC_CUSTOM_DOMAIN', '')
 AWS_DEFAULT_ACL = None  # Uses buckets security access policies
 AWS_QUERYSTRING_AUTH = os.environ.get(
     # This stops signature/auths from appearing in saved URLs

src/utils/storage.py

@@ -12,6 +12,7 @@
 
         class PublicStorageClass(S3Boto3Storage):
             bucket_name = getattr(settings, "AWS_STORAGE_BUCKET_NAME", None)
+            custom_domain = getattr(settings, "AWS_S3_PUBLIC_CUSTOM_DOMAIN", "")
 
         class PrivateStorageClass(S3Boto3Storage):
             bucket_name = getattr(settings, "AWS_STORAGE_PRIVATE_BUCKET_NAME", None)