Fix coder encode decode javadoc

[Subramanya-Veeregowda]

Improved Javadoc for Context in Coder class.

• Added proper summary line to satisfy Checkstyle
• Clarified OUTER vs NESTED usage with examples
• Fixed formatting and @deprecated usage

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Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request primarily focuses on enhancing documentation across two key areas: improving the Javadoc for the Coder class in Java to clarify the usage and purpose of Context in encoding and decoding operations, and expanding the Python programming guide with new examples for advanced field selection patterns. The changes aim to provide clearer guidance and better understanding for developers using these functionalities.

Highlights

• Improved Javadoc for Coder.Context: The Javadoc for the Coder.Context class has been significantly enhanced, including a proper summary line, clearer explanations of OUTER vs NESTED contexts, and practical usage examples. Redundant Javadoc for individual fields within Context was removed as the class-level documentation now covers their meaning.
• Enhanced Coder encode and decode Javadoc: The Javadoc for both the encode and decode methods in the Coder class has been updated. This includes better descriptions of how values are handled, the importance of boundary information for multiple elements, and how Context influences encoding/decoding. The @deprecated messages for context-aware methods were also refined.
• Added Python SDK documentation examples: New examples have been added to the programming guide for the Python SDK, demonstrating how to use wildcard selection for nested fields, select nested fields within arrays, and select specific keys from map fields.

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