As part of issue #15344, the error report emails add the user role
information. This commit adds the user role information to be used
by sentry as well.
Use the default configuration, which catches Error logging and
exceptions. This is placed in `computed_settings.py` to match the
suggested configuration from Sentry[1], which places it in `settings.py`
to ensure it is consistently loaded early enough.
It is placed behind a check for SENTRY_DSN soas to not incur the
additional overhead of importing the `sentry_sdk` modules if Sentry is
not configured.
[1] https://docs.sentry.io/platforms/python/django/