feat: proxy and custom SSL certificates support

[jansimonb]

Closes #139

Proposed Changes

• Add SSLRootsFilePath field into ClientConfig to configure additional SSL root certificates
• Add Proxy field into ClientConfig to set proxy URL

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 91.42857% with 6 lines in your changes missing coverage. Please review.

Project coverage is 91.29%. Comparing base (ed5a8a0) to head (46a1181).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
influxdb3/client.go	94.00%	2 Missing and 1 partial ⚠️
influxdb3/query.go	85.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #141      +/-   ##
==========================================
+ Coverage   91.15%   91.29%   +0.14%     
==========================================
  Files          16       16              
  Lines        1356     1413      +57     
==========================================
+ Hits         1236     1290      +54     
- Misses         91       93       +2     
- Partials       29       30       +1     

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[karel-rehor]

Everything committed to here looks good. Tests pass locally for me. However it might be useful to have an example of using the new configuration properties SSLRootsFilePath and Proxy in examples_test.go (https://github.com/InfluxCommunity/influxdb3-go/blob/main/influxdb3/example_test.go).

I believe they will then render in the go package repository. https://pkg.go.dev/github.com/InfluxCommunity/influxdb3-go/v2/influxdb3#example-New

It has been a while since I've made these kinds of updates to go but if I recall correctly, this is where such doc examples can be added.

[karel-rehor]

Looks good.