---
features:

  - Provides API 2.18, which makes the use of project_ids in API urls
    optional.

upgrade:

  - In order to make project_id optional in urls, we must constrain
    the set of allowed values for project_id in our urls. This
    defaults to a regex of ``[0-9a-f\-]+``, which will match hex uuids
    (with / without dashes), and integers. This covers all known
    project_id formats in the wild.

    If your site uses other values for project_id, you can set a site
    specific validation with ``project_id_regex`` config variable.
