feat: support for binary DOUBLE and ARRAY[DOUBLE]

[nwoolmer]

Upgrades the .NET client to for QuestDB OSS 9.0.0.

Changelist:

• Refactor ISender into V1 and V2 versions.
• Refactor Buffer into V1 and V2 versions, and add interface IBuffer.
• Introduce array overloads to support sending multidimensional double arrays.
• Introduce override to send doubles in binary format.
• Introduce new protocol_version parameter, including automatic negotation if set to auto.
• Add Nullable API to streamline sending nulls to QuestDB.

TODO in future PRs:

• Support AoT compilation (compatibility fixes)
• Introduce SenderPool which supports an API allowing you to send Buffers individually.

[Copilot]

Pull Request Overview

Adds support for binary DOUBLE and ARRAY[DOUBLE] in the .NET client and introduces protocol versioning (V1/V2) with auto-negotiation.

• Refactor ISender and IBuffer into V1/V2 versions and add new overloads for multidimensional double arrays and binary doubles.
• Add a protocol_version option (with an “auto” setting that negotiates on HTTP) and a factory method for creating the right buffer type.
• Update TcpSender and HttpSender to use the new buffer factory and protocol V2 features.

Reviewed Changes

Copilot reviewed 50 out of 51 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/net-questdb-client/Senders/ISender.cs	Split ISender into V1/V2 interfaces and added array/binary overloads
src/net-questdb-client/Utils/SenderOptions.cs	Added protocol_version support and config-key validation set
src/net-questdb-client/Buffers/Buffer.cs	Replaced Buffer implementation with a static factory
src/net-questdb-client/Buffers/BufferV2.cs	Implemented V2-level binary DOUBLE and ARRAY support
src/net-questdb-client/Senders/HttpSender.cs	Added HTTP negotiation for protocol version and use of new buffers
src/net-questdb-client/Senders/TcpSender.cs	Updated to use new buffer factory and V2 features

Comments suppressed due to low confidence (5)

src/net-questdb-client/Utils/SenderOptions.cs:50

• The field keySet should be PascalCase (KeySet) to match C# naming conventions for static fields.

    private static readonly HashSet<string> keySet = new()

src/net-questdb-client/Utils/SenderOptions.cs:72

• Public properties should use PascalCase; consider renaming protocol_version to ProtocolVersion to follow C# conventions.

    private ProtocolVersion _protocol_version = ProtocolVersion.Auto;

src/net-questdb-client/Sender.cs:84

• [nitpick] Throwing NotImplementedException for unsupported protocols can be confusing; consider using NotSupportedException to clearly indicate unsupported protocol values.

        throw new NotImplementedException();

src/net-questdb-client-tests/BufferTests.cs:3

• This test class is empty; add unit tests for the new BufferV2 implementation and the Buffer.Create factory method to ensure binary and array support work as expected.

public class BufferTests

src/net-questdb-client/Utils/SettingsResponse.cs:111

• [nitpick] The XML summary for the Preferences record is incomplete; consider expanding the description beyond "Contains" to explain what preferences are represented.

/// <summary>

[ideoma]

A few questions about the approach

[ideoma]

Thanks for the contribution!

[nwoolmer]

Thanks for bringing this over the line @ideoma !