importers/shaarli_api: allow fetching shaarli data from the API directly (no external call to shaarli-client)

[nodiscc]

# if shaarli_api_url/secret are not provided, the source_file must be created using python-shaarli-client https://python-shaarli-client.readthedocs.io/
module_options:
  shaarli_api_url: https://shaarli.example.org # shaarli instance URL
  shaarli_api_secret: CHANGEME # API secret
  shaarli_api_insecure: False # (default False) bypass API SSL/TLS certificate verification
  shaarli_api_visibility: all # (all/public/private, default all) only get shaares with this visibility status
  source_file: shaarli-export.json # JSON file to store shaarli API response to/import data from