fix: serialization of dataframes with NaN values and columns starting with digits

[fdorssers]

Closes #485

Proposed Changes

Update the regex string that's supposed to remove spurious leading commas in case the first field is None/NaN by also checking whether the first character of a column is a digit.

Locally pytest tests wasn't able to complete successfully due to an error in InfluxDBClientAsyncTest.test_delete_api. But I'm assuming that's due to a setup issue.

Checklist

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

[codecov-commenter]

Codecov Report

Merging #486 (9ba3d6a) into master (3842a9e) will not change coverage.
The diff coverage is 100.00%.

❗ Current head 9ba3d6a differs from pull request most recent head 521e53a. Consider uploading reports for the commit 521e53a to get more accurate results

@@           Coverage Diff           @@
##           master     #486   +/-   ##
=======================================
  Coverage   89.42%   89.42%           
=======================================
  Files          39       39           
  Lines        3347     3347           
=======================================
  Hits         2993     2993           
  Misses        354      354           

Impacted Files	Coverage Δ
...fluxdb_client/client/write/dataframe_serializer.py	98.26% <100.00%> (ø)

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[bednar]

Thank you very much for your PR 👍

There is only one requirement about README.md before we are be able merge your PR:

[bednar]

@fdorssers thanks again for the PR 👍

LGTM 🚀

[fdorssers]

No problem! Been using Influx for a while now, glad to contribute something back! 🥳

[powersj]

Thank you for the fix and a test!