fix: reduce agenda data calculation time

[rjsparks]

This intentionally leaves a commented out debug statement. Against main without #4621, it will report differences with the secretariat group. It will report equal once #4621 is in place.

I had done the work to precalculate the order in the view, but while investigating what led to #4621, discovered that the calculations had already been made and attached to the objects.

It's not clear why it wasn't being used.

[codecov]

Codecov Report

Merging #4622 (438bf29) into main (cbf3431) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 438bf29 differs from pull request most recent head 63f9b17. Consider uploading reports for the commit 63f9b17 to get more accurate results

@@            Coverage Diff             @@
##             main    #4622      +/-   ##
==========================================
- Coverage   88.39%   88.39%   -0.01%     
==========================================
  Files         296      296              
  Lines       39741    39707      -34     
==========================================
- Hits        35130    35098      -32     
+ Misses       4611     4609       -2     

Impacted Files	Coverage Δ
ietf/help/urls.py	100.00% <ø> (ø)
ietf/ietfauth/views.py	91.04% <ø> (+0.25%)	⬆️
ietf/meeting/views.py	90.52% <ø> (ø)
ietf/doc/views_draft.py	91.94% <100.00%> (+0.04%)	⬆️
ietf/ietfauth/forms.py	95.10% <100.00%> (+0.26%)	⬆️
ietf/person/models.py	91.91% <100.00%> (+0.75%)	⬆️
ietf/person/utils.py	86.98% <100.00%> (ø)
ietf/utils/pipe.py	82.60% <0.00%> (-4.35%)	⬇️
ietf/utils/mail.py	79.62% <0.00%> (-0.47%)	⬇️
ietf/doc/views_search.py	88.81% <0.00%> (-0.42%)	⬇️

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[jennifer-richards]

This looks fine.

It is possible for a session to have order_number = None if session.group is None. I don't think those should be showing up in the schedules, but it might cause bad links if it does. Could fall back to 0 if it comes up instead of propagating the None.

Other thought - it'd be good to update the comment on preprocess_assignments_for_agenda() to document that it's setting the order_number.

[rjsparks]

It is possible for a session to have order_number = None if session.group is None. I don't think those should be showing up in the schedules, but it might cause bad links if it does. Could fall back to 0 if it comes up instead of propagating the None.

Session is defined such that Django will not allow session.group to be None.