fix: only send state change notifications once

[jennifer-richards]

This avoids sending multiple copies of a state change notification to a CommunityList subscriber. This is accomplished by checking whether created is True in the call to our signal handler. (Relevant Django docs)

Refactors the rfceditor sync code where we were triggering the double notifications to do its updates before the save() call.

The refactoring would resolve the issue without the check of the created flag in our signal handler, but I think the guard is worth it. I did a fairly thorough but probably not exhaustive skim for other places where we might save a DocEvent twice and did not find any.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.83%. Comparing base (c7f6bde) to head (46b4131).
Report is 76 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7953      +/-   ##
==========================================
+ Coverage   88.78%   88.83%   +0.04%     
==========================================
  Files         296      304       +8     
  Lines       41320    41517     +197     
==========================================
+ Hits        36687    36882     +195     
- Misses       4633     4635       +2     

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