Clarify documentation about lifetimes of the events and attributes

[Mingun]

Use self-describing lifetime names

Closes #331

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 64.28571% with 20 lines in your changes missing coverage. Please review.
✅ Project coverage is 55.28%. Comparing base (e00ae5c) to head (e5c2e30).
⚠️ Report is 63 commits behind head on master.

Files with missing lines	Patch %	Lines
src/events/mod.rs	64.28%	20 Missing ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1006      +/-   ##
==========================================
- Coverage   57.31%   55.28%   -2.04%     
==========================================
  Files          46       51       +5     
  Lines       18197    18721     +524     
==========================================
- Hits        10429    10349      -80     
- Misses       7768     8372     +604     

Flag	Coverage Δ
unittests	55.28% <64.28%> (-2.04%)	⬇️

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