Stability changes for version 5.0.0

[amunra]

Overview

This PR is about introducing stability changes targeting the release of version 5.0.0.

Task list

• @javier: Updated front page doc and examples that are consistent across all clients.
• JSON-driven array tests
• Reword doc sections around protocol version, make it clear that selecting the protocol
  is only suggested for TCP and we advise "auto" for HTTP.
• Add a test for max_line_len from /settings (see point above).
• Introduce a new simpler array C API that doesn't require strides:
  line_sender_buffer_column_f64_arr_row_major (we will use this from Python).
• Investigate if the two APIs that take strides can be optimised further.
  You mentioned that these are slower than the equivalent Rust ndarray APIs.
• Consolidate array error codes into a single ArrayError code. These should be consolidated:
  • ArrayHasTooManyDims
  • ArrayViewError
  • ArrayWriteToBufferError
• Introduce a lower-level C++ API that just takes pointers and lengths for
  data and strides.
• Introduce an overloaded C++ API that just takes an array data pointer and
  length, and assumes default strides (calling _f64_arr_row_major).
• Fix warnings when generating docs with (cd questdb-rs && cargo doc --open)
  E.g.: warning: unresolved link to Sender::new_buffer_with_max_name_len.
• Add the C++ API change from PR Implement C++ line_sender::flush_and_keep_with_flags() #88
• Update and document (front page + examples + api docs) which is the first
  version of QuestDB supports arrays.
  My guess is that it is going to be 8.4.0, but we need to confirm this.
  (I've also added this todo to the Python client TODO list.)
• Improved C++ API ergonomics:
  • Lower-level API that is similar to the C API
  • Higher-level API that takes a vectors and spans in C++20.
• Once the next QuestDB release is cut, we should revert the CI hacks that test
  against the nd_arr branch. We should also retain a CI test run that runs
  against an older version of QuestDB (e.g. 8.3.3) to ensure that we don't
  introduce regressions against protocol version 1.
• Revise MAX_ARRAY_BUFFER_SIZE: lower it!

Tandem PR

See related py-questdb-client PR: questdb/py-questdb-client#108

[Copilot]

Pull Request Overview

This PR introduces various stability improvements for version 5.0.0, including updated array APIs for both C and C++ clients, consolidated error codes for array handling, and enhancements to protocol version negotiation and documentation.

• Updated test cases and API calls to work with the new array C API and C++ ergonomics for array ingestion.
• Consolidated error codes into a single ArrayError and updated related documentation and examples.
• Adjusted the default maximum name length handling and improved consistency across FFI, Rust, and documentation.

Reviewed Changes

Copilot reviewed 45 out of 48 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
system_test/test.py	Updates DEFAULT_ARRAY_RELEASE version and adds new tests for default max name length and array API examples.
system_test/questdb_line_sender.py	Introduces a new simpler C-major array API and modifies pointer casts accordingly.
questdb-rs/src/tests/*	Updates tests to use the consolidated ArrayError instead of multiple array-related errors.
questdb-rs/src/ingress/*	Updates API implementations and documentation for array ingestion, error code changes, and protocol version support.
questdb-rs/examples/*	Updates examples to reflect the new array API usage and clarifies the QuestDB server version requirements.
questdb-rs-ffi/*	Adjusts FFI bindings and macros to support the new array API (e.g., using c_double_p).
doc/*	Revises documentation and release notes to reference new protocols, API changes, and default settings.
CMakeLists.txt & bumpversion files	Update version references and compile instructions for the 5.0.0 release.

Comments suppressed due to low confidence (1)

questdb-rs/src/ingress/mod.rs:624

• The constant MAX_NAME_LEN_DEFAULT is defined as 127, but the documentation comment mentions a default limit of 32. Please update the comment to match the actual constant value to ensure consistency.

    /// For the default max name length limit (32), use [`Self::new`].