Refactor downloads

[dpieski]

Summary

Refactors download functionality across all clients, adds session sharing, and fixes model inconsistencies.

Changes

Download Architecture

• Added download_file() and download_archive() base methods in BaseUSPTOClient
• Added save_response_to_file() helper for file saving with overwrite protection
• Standardized download behavior across Patent Data, PTAB Trials, PTAB Appeals, PTAB Interferences, and Petition Decisions clients
• Added USPTODownloadError exception

Session Sharing

• Clients sharing the same USPTOConfig instance now share HTTP sessions
• Added context manager support for automatic resource cleanup
• Added close() method for manual session cleanup

Configuration

• Added download_chunk_size parameter to HTTPConfig (default: 8192 bytes)
• Streaming downloads with configurable buffer sizes

Pagination

• Enhanced paginate_results() to support both GET and POST methods via post_body parameter
• paginate_decisions() now uses POST for complex queries
• Automatic offset/limit management for POST bodies

Model Changes

Patent Data Models

• Changed PatentFileWrapper.application_number_text from str | None = None to str (required)
• Defaults to empty string when missing from API response
• Added DocumentMimeType enum
• Added Document.has_format() and Document.get_format() methods
• Added DocumentBag.filter_by_format() method

PTAB Models

• Restored documentCategory field in TrialDocumentData
• Properly serialized in to_dict() and deserialized in from_dict()

Error Handling

• POST request bodies now included in error messages
• Improved error context for debugging

Tests

• Added download tests for all clients
• Added PTAB download integration tests
• Fixed PTAB Appeals fixture scope from function to class

Commits

• c1fba98 update tests based on document class improvements
• 176de5a refactor downloads
• 6ab1224 Update tests and README examples
• 0cd0057 improve paginate_decisions with POST support
• 548df75 Configurable Download Chunk Size
• 6d4088b implement session sharing

Related Issues

Closes #27