chore(dev): allow passwordless login for dev

[jennifer-richards]

Completely bypasses password check instead of counting on the password being replaced in the DB dump. In a world where Datatracker uses OIDC for login and no longer maintains its own passwords, this will continue to allow login. To make this work, we'll also need to expose the traditional Django login instead of or parallel to the OIDC login views.

Continues to allow login using any email address.

To prevent accidental use in production, only configures the backend via settings_local.py in dev environments for now. A guard in the backend class throws an exception if it's used in other than development and test modes. That will prevent accidental use, even if we deploy this to the sandbox k8s environment where a misconfiguration could more plausibly enable this for production.

[codecov]

Codecov Report

❌ Patch coverage is 31.81818% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.63%. Comparing base (22c808c) to head (21dabcc).
⚠️ Report is 19 commits behind head on main.

Files with missing lines	Patch %	Lines
ietf/ietfauth/backends.py	31.81%	15 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #11573      +/-   ##
==========================================
- Coverage   88.65%   88.63%   -0.03%     
==========================================
  Files         333      333              
  Lines       44966    44984      +18     
==========================================
+ Hits        39866    39871       +5     
- Misses       5100     5113      +13     

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