FEAT: Support correct type handling of None parameters in parameter binding

[gargsaumya]

Work Item / Issue Reference

AB#38339

GitHub Issue: #<ISSUE_NUMBER>

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Summary

This pull request adds support for using the SQLDescribeParam ODBC API to determine the correct SQL type for parameters with unknown types (such as None values), improving parameter binding accuracy—especially for binary columns. The changes include adding the necessary function pointer, loading it from the driver, and updating the parameter binding logic to call SQLDescribeParam when needed.

ODBC API Integration:

• Added the SQLDescribeParamFunc typedef and declared/defined the SQLDescribeParam_ptr function pointer to enable calling SQLDescribeParam from the driver. [1] [2] [3] [4] [5]

Parameter Binding Improvements:

• Updated the logic in BindParameters to call SQLDescribeParam for parameters with unknown types, ensuring correct SQL type, column size, and decimal digits are used for None values and improving support for binary columns.

Minor Cleanups:

• Removed a TODO comment in _map_sql_type as type detection is now handled more robustly.

[Copilot]

Pull Request Overview

This PR adds support for using the ODBC SQLDescribeParam API to properly handle parameter binding for None values, particularly improving type detection for binary columns. Previously, None parameters used a default SQL type which could cause issues with binary columns.

• Added ODBC SQLDescribeParam function pointer integration to query parameter metadata
• Updated parameter binding logic to call SQLDescribeParam when parameter type is unknown
• Removed TODO comment related to binary column handling since the issue is now resolved

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
mssql_python/pybind/ddbc_bindings.h	Added SQLDescribeParam function typedef and pointer declaration
mssql_python/pybind/ddbc_bindings.cpp	Implemented SQLDescribeParam loading and parameter binding logic using the API
mssql_python/cursor.py	Removed TODO comment about adding SQLDescribeParam support

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[sumitmsft]

Looks good to me.