various fixes

- use signed url for s3 downloads
- re-arrange tar.gz file to match original
- delete all working files after tarring
- import from s3 export

TODO

- check local export and import
- fix error when avatar missing
- deal with multiple s3 storage options (e.g. Azure)

.env.example

@@ -81,6 +81,7 @@ AWS_SECRET_ACCESS_KEY=
 # AWS_S3_CUSTOM_DOMAIN=None       # "example-bucket-name.s3.fr-par.scw.cloud"
 # AWS_S3_REGION_NAME=None         # "fr-par"
 # AWS_S3_ENDPOINT_URL=None        # "https://s3.fr-par.scw.cloud"
+# S3_ENDPOINT_URL=None            # same as AWS_S3_ENDPOINT_URL - needed for non-AWS for user exports
 
 # Commented are example values if you use Azure Blob Storage
 # USE_AZURE=true