feat: support partial writes

[alespour]

Proposed Changes

This PR adds partial-write support in the C# client and finalizes write API selection behavior for product compatibility.

Feature highlights:

• Adds structured partial-write errors via InfluxDBPartialWriteException with per-line details:
  • LineNumber
  • ErrorMessage
  • OriginalLine
• AcceptPartial defaults to true (server default behavior)
• accept_partial=false is sent only when partial writes are explicitly disabled
• UseV2Api routes writes between:
  • V2 API endpoint: /api/v2/write
  • V3 API endpoint: /api/v3/write_lp

Default behavior and option semantics:

• Default writes use the V2 API endpoint (UseV2Api=true).
• NoSync requires UseV2Api=false and is rejected otherwise.
• AcceptPartial applies only to V3 endpoint writes and is ignored on V2 endpoint writes.

Configuration surfaces:

• Write options: AcceptPartial, UseV2Api, NoSync
• Connection string: writeAcceptPartial, writeUseV2Api, writeNoSync
• Environment variables: INFLUX_WRITE_ACCEPT_PARTIAL, INFLUX_WRITE_USE_V2_API, INFLUX_WRITE_NO_SYNC

See Partial writes for reference.

Example (partial-write handling):

try
{
    await client.WriteRecordAsync(lp);
}
catch (InfluxDBPartialWriteException e)
{
    foreach (var lineErr in e.LineErrors)
    {
        Console.WriteLine($"line {lineErr.LineNumber} failed: {lineErr.ErrorMessage} ({lineErr.OriginalLine})");
    }
}
catch (InfluxDBApiException e)
{
    Console.WriteLine(e.Message);
}

Example (enable V3 write options):

using var client = new InfluxDBClient(new ClientConfig
{
    Host = host,
    Token = token,
    Database = database,
    WriteOptions = new WriteOptions
    {
        UseV2Api = false,
        NoSync = true,
        AcceptPartial = false
    }
});

await client.WriteRecordAsync(lp);

Checklist

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

[Copilot]

Pull request overview

This PR adds partial-write support to the C# client (including structured per-line error details) and finalizes write routing behavior between InfluxDB’s V2 and V3 write endpoints for product compatibility.

Changes:

• Introduces InfluxDBPartialWriteException and JSON error parsing to surface v3 partial-write line errors.
• Adds write routing/behavior controls via WriteOptions (UseV2Api, AcceptPartial, NoSync) plus connection string/env var configuration.
• Updates tests and docs to reflect default V2 routing and explicit V3 option behavior.

Reviewed changes

Copilot reviewed 12 out of 14 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
README.md	Documents partial writes and explains default V2 routing + configuration surfaces.
Client/Internal/RestClient.cs	Parses JSON error bodies; throws InfluxDBPartialWriteException with structured line errors on v3 partial-write responses.
Client/InfluxDBPartialWriteException.cs	Adds new exception type carrying per-line partial-write error details.
Client/InfluxDBClient.cs	Routes writes to /api/v2/write by default and applies v3-only query params (no_sync, accept_partial) when using v3.
Client/Config/WriteOptions.cs	Adds AcceptPartial/UseV2Api options and validates NoSync usage.
Client/Config/ClientConfig.cs	Adds connection string/env parsing for writeAcceptPartial and writeUseV2Api.
Client/Client.csproj	Adds System.Text.Json dependency for JSON parsing.
Client.Test/Internal/RestClientTest.cs	Adds/updates tests for partial-write error parsing and typed/untyped fallback behavior.
Client.Test/InfluxDBClientWriteTest.cs	Updates tests for default V2 routing, explicit V3 routing, and option validation/guidance messages.
Client.Test/InfluxDBClientHttpsTest.cs	Formatting-only change.
Client.Test/InfluxDBApiExceptionTest.cs	Formatting-only change.
Client.Test/Config/ClientConfigTest.cs	Extends tests to cover new connection string/env write options.
Client.Test.Integration/WriteTest.cs	Refactors exception check using pattern matching.
CHANGELOG.md	Adds unreleased feature entry for partial writes + default V2 routing.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Pull request overview

Copilot reviewed 13 out of 15 changed files in this pull request and generated 4 comments.

[Copilot]

Pull request overview

Copilot reviewed 13 out of 15 changed files in this pull request and generated 4 comments.

Comments suppressed due to low confidence (1)

Client/InfluxDBClient.cs:848

• This guidance error message starts with a lowercase "server" while other user-facing exceptions in the client are capitalized (e.g., "Cannot write..."). Consider capitalizing this message for consistency.

                    throw new InfluxDBApiException(
                        $"server doesn't support the V3 API endpoint (/api/v3/write_lp) " +
                        $"(set UseV2Api=true; write options: {{UseV2Api:false,NoSync:{writeOptions.NoSync.ToString().ToLowerInvariant()},AcceptPartial:{writeOptions.AcceptPartial.ToString().ToLowerInvariant()}}})",
                        ex.HttpResponseMessage!);

[Copilot]

Pull request overview

Copilot reviewed 13 out of 15 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 13 out of 15 changed files in this pull request and generated 1 comment.