fix: Honor struct tags on WriteData and avoid panic for unexported fields

[srebhan]

Proposed Changes

In the current implementation, the WriteData function will check the tagged structure before processing it. This has the drawback that the function will error out for invalid fields even though those fields are not meant to be exported by either being tagged lp:"-" or by not being tagged at all.

Furthermore, the current code panics for unexported fields because Interface() will panic on those fields (see documentation).

This PR moves the structure checks to a point where we can be sure that the field needs to be exported. Furthermore, the PR handles tagged unexported fields without panic.

Checklist

• CHANGELOG.md updated
• Rebased/mergeable
• A test has been added if appropriate
• Tests pass
• Commit messages are conventional
• Sign CLA (if not already signed)

[codecov]

Codecov Report

Attention: Patch coverage is 69.23077% with 16 lines in your changes missing coverage. Please review.

Project coverage is 81.02%. Comparing base (5666748) to head (db9ecb2).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
influxdb3/write.go	69.23%	14 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #113      +/-   ##
==========================================
- Coverage   86.12%   81.02%   -5.10%     
==========================================
  Files          15       14       -1     
  Lines        1211     1186      -25     
==========================================
- Hits         1043      961      -82     
- Misses        139      195      +56     
- Partials       29       30       +1     

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[vlastahajek]

@srebhan, thank you for the PR and the fix. Great job! 👍
Are you going to fix the reported check failures?

[bednar]

@vlastahajek, the linter is fixed and CHANGELOG.md has been updated. Please take a look for the final review.