Added AWS_S3_CUSTOM_DOMAIN

This setting is necessary to avoid django-storages applying a security token to S3 URLs.

ECOM-4081

lms/envs/aws.py

@@ -445,6 +445,7 @@ AWS_STORAGE_BUCKET_NAME = AUTH_TOKENS.get('AWS_STORAGE_BUCKET_NAME', 'edxuploads
 # Disabling querystring auth instructs Boto to exclude the querystring parameters (e.g. signature, access key) it
 # normally appends to every returned URL.
 AWS_QUERYSTRING_AUTH = AUTH_TOKENS.get('AWS_QUERYSTRING_AUTH', True)
+AWS_S3_CUSTOM_DOMAIN = AUTH_TOKENS.get('AWS_S3_CUSTOM_DOMAIN', 'edxuploads.s3.amazonaws.com')
 
 if AUTH_TOKENS.get('DEFAULT_FILE_STORAGE'):
     DEFAULT_FILE_STORAGE = AUTH_TOKENS.get('DEFAULT_FILE_STORAGE')