fix: switch to staging

fix: support filtering properly

- initialize criteria properly
- add guard to filter in case something invalid was entered and
parsed by wagtail (e.g., foo:error)

fix: use appropriate formatter

start_date and end_date are strings, not date objects

deps: upgrade to wagtail 2.13

TODO: upgrade to django 3.2 after backwards incompatibility checks and
testing

https://docs.djangoproject.com/en/3.2/releases/3.2/

feat: add contributed models to profile->models

closes comses#549

deps: bump to wagtail 2.11.2

start to clean up membership rubric

add SGCI logo to footer acknowledgements

fix(build): improve staging deployment

staging includes elasticsearch2 which wasn't getting updated when we
bump versions

[skip ci]

refactor: clean up nginx staging|prod configs