Move populate_by_name to Event model

[johannaengland]

Scope and purpose

Inspired by a meeting about Pydantic aliases today. That way not every model using aliases needs to explicitly declare it.

Reference to what populate_by_name does: https://docs.pydantic.dev/latest/api/config/#pydantic.config.ConfigDict.populate_by_name

Related to #338, #335 and #352.

Contributor Checklist

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• Added a changelog fragment for towncrier
  • just internal changes
• Added/amended tests for new/changed code
• Added/changed documentation
• Linted/formatted the code with black, ruff and isort, easiest by using pre-commit
• The first line of the commit message continues the sentence "If applied, this commit will ...", starts with a capital letter, does not end with punctuation and is 50 characters or less long. See https://cbea.ms/git-commit/
• If applicable: Created new issues if this PR does not fix the issue completely/there is further work to be done

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.57%. Comparing base (419305a) to head (99d266a).
Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #357      +/-   ##
==========================================
- Coverage   98.57%   98.57%   -0.00%     
==========================================
  Files          77       77              
  Lines        9701     9699       -2     
==========================================
- Hits         9562     9560       -2     
  Misses        139      139              

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