feat(metadata): make af closable by default

[christophe-ramet]

closes #4054

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.24%. Comparing base (92fa7a8) to head (f9409b7).

Additional details and impacted files

@@                           Coverage Diff                           @@
##           disallow_update_delete_on_closed_af    #4055      +/-   ##
=======================================================================
- Coverage                                86.24%   86.24%   -0.01%     
=======================================================================
  Files                                      137      137              
  Lines                                    10912    10829      -83     
=======================================================================
- Hits                                      9411     9339      -72     
+ Misses                                    1501     1490      -11     

Flag	Coverage Δ
pytest	86.24% <ø> (-0.01%)	⬇️

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