fix: write API defaults

[alespour]

Proposed Changes

Aligns Rust client behaviour with the rest - switches the default write endpoint to v2 for broader InfluxDB 3 family compatibility.

Details:

• Default changed (use_v2_api: true): writes now use V2 API endpoint (/api/v2/write) by default, making the client compatible with InfluxDB Clustered and InfluxDB Cloud Serverless/Dedicated by default. This change align the behaviour of Rust client with others. Set use_v2_api(false) to use the v3 endpoint.
• Validation: no_sync=true with use_v2_api=true is now a config error — no_sync is a v3-only feature, caught at build time and at write execution time. Alignment, again.
• New builder methods: write_use_v2_api, write_accept_partial, write_no_sync on ClientConfigBuilder for easier instantiation.

Note to reviewers: v0.2.0 will be the first public relase (0.1.0 version was only published to crates.io just to set up infrastructure), so the changes are not really breaking.

Checklist

• CHANGELOG.md updated
• Rebased/mergeable
• A test has been added if appropriate
• Tests pass
• Commit messages are conventional

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.45%. Comparing base (dbe56b7) to head (1bbd4ca).

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #19      +/-   ##
==========================================
+ Coverage   83.41%   83.45%   +0.03%     
==========================================
  Files          10       10              
  Lines        1815     1837      +22     
==========================================
+ Hits         1514     1533      +19     
- Misses        301      304       +3     

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[Copilot]

Pull request overview

Aligns the Rust client’s default write behavior with other clients by switching the default write endpoint to the V2 compatibility API (/api/v2/write), improving out-of-the-box compatibility across the InfluxDB 3 family. It also adds configuration validation to prevent V3-only options (notably no_sync) from being used with the V2 endpoint.

Changes:

• Switch WriteOptions default to use_v2_api = true and add validation enforcing no_sync requires use_v2_api=false.
• Add ClientConfigBuilder convenience setters: write_use_v2_api, write_accept_partial, write_no_sync.
• Update tests and documentation to reflect the new defaults and constraints.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/write.rs	Defaults writes to V2 endpoint and introduces WriteOptions::validate() for incompatible option detection.
src/config.rs	Adds builder helpers for common write defaults and validates write options during config build.
src/client.rs	Validates per-request write options at execution time to catch invalid overrides (e.g., .no_sync() under V2).
tests/write_tests.rs	Updates write tests for new default endpoint and adds a test asserting no_sync requires V3.
tests/retry_tests.rs	Ensures retry tests explicitly use V3 to preserve existing test expectations.
tests/config_tests.rs	Adds coverage for new default + builder helpers and validates invalid no_sync/V2 combinations.
README.md	Updates version/examples and documents environment/connection-string write defaults and endpoint compatibility.
CHANGELOG.md	Documents the default endpoint change and V3-only behavior constraints.

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[bednar]

LGTM 🚀