Feat/data export functionality

[LifeJiggy]

Summary

This PR adds a DataExporter utility class that enables easy export of API response data to JSON and CSV formats, helping developers analyze and persist API responses.

Problem

Developers often need to export API response data for analysis, reporting, or persistence, but currently have no built-in way to do this. This leads to:

• Manual data transformation and export logic
• Difficulty analyzing API response patterns
• No standardized way to persist response data
• Time-consuming data processing for reports

Solution

Add DataExporter class with:

• JSON export with proper formatting and file saving
• CSV export with automatic data flattening
• Support for nested response structures
• Both string output and file saving capabilities
• Custom header support for CSV export

Key Features

• JSON Export: Clean JSON formatting with file saving
• CSV Export: Automatic flattening of nested data
• Nested Data Support: Handles complex API response structures
• File Operations: Direct saving to files with proper encoding
• Flexible Output: Both string and file output options
• Standard Library: No external dependencies

Benefits

• Simplifies data export and analysis workflows
• Enables easy data persistence and sharing
• Supports standard data formats (JSON/CSV)
• Handles complex nested API responses
• Improves data analysis capabilities

Testing

Added comprehensive test suite covering:

• JSON export to string and file
• CSV export to string and file
• Nested data flattening
• File operations and encoding
• Edge cases and error conditions

All tests pass with full coverage of export functionality.

Usage Examples

from gradient._utils import DataExporter

exporter = DataExporter()

# Export API response to JSON
response = client.models.list()
json_data = exporter.export_json(response)
# Or save to file
exporter.export_json(response, "models.json")

# Export to CSV for analysis
models_data = [
    {"name": "llama3.3-70b", "context_length": 8192},
    {"name": "llama3-8b", "context_length": 4096}
]
csv_data = exporter.export_csv(models_data)
# Or save to file
exporter.export_csv(models_data, "models.csv")