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

Every pull request should have this checklist filled out, no matter how small it is. More information about contributing to Zino can be found in the README.

• [ ] Added a changelog fragment for towncrier
  • just internal changes
• [ ] Added/amended tests for new/changed code
• [ ] Added/changed documentation
• [X] Linted/formatted the code with black, ruff and isort, easiest by using pre-commit
• [X] 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[bot]]

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[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

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

Additional details and impacted files

```diff @@ 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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