swh-docs: Unstuck build

A recent new module got added. But nothing specifically got done in regards to the documentation. This now fails with the following:

...
Exception occurred:
  File "/home/jenkins/workspace/DDOC/publish/swh-docs/.tox/sphinx/lib/python3.7/site-packages/swh/deposit/models.py", line 18, in <module>
    from swh.auth.django.models import OIDCUser
ModuleNotFoundError: No module named 'swh.auth'
...
ERROR: InvocationError for command '/home/jenkins/workspace/DDOC/publish/swh-docs/.tox/sphinx/bin/python -m pifpaf run postgresql -- make -C docs html' (exited with code 2)

Investigate and fix and maybe check to update the docs when we bootstrap new modules.

• [1] https://jenkins.softwareheritage.org/view/all/job/DDOC/job/publish/888/

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Migrated from T3172 (view on Phabricator)