Added setting WEBMENTIONS_USE_CELERY (boolean, default True)

• If False:
  • celery does not need to be installed
  • New models PendingIncomingWebmention and PendingOutgoingContent are created to store the required data for later batch-processing.
  • New management command: manage.py pending_mentions can be used to process these data.

/get endpoint:

• Now returns results for SimpleMention objects as well as Webmentions.
• Added field type with value webmention or simple so they can be differentiated when displaying.

Updated instructions for installation with or without celery.