feat: only store real date changes in history

[rudimatz]

avoid changes of published time recorded within one second

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 88.51%. Comparing base (d51c909) to head (1fec2c8).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
ietf/api/serializers_rpc.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #10865   +/-   ##
=======================================
  Coverage   88.51%   88.51%           
=======================================
  Files         332      332           
  Lines       44974    44970    -4     
=======================================
- Hits        39808    39806    -2     
+ Misses       5166     5164    -2     

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[rudimatz]

keep as draft until bug is verified after cutover