Generate OpenAPI schema file from parsed entities and methods

[Copilot]

This PR implements OpenAPI 3.0.3 schema generation from the parsed Mastodon entities and API methods. The implementation converts the parsed documentation into a complete OpenAPI specification output in JSON format.

Key Features

• OpenAPI Schema Generation: New OpenAPIGenerator class that converts parsed entities and methods into OpenAPI 3.0.3 format
• Entity Conversion: Transforms 64 Mastodon entities into OpenAPI schema components with proper type mapping
• API Method Conversion: Converts 165 API methods across 40 method files into OpenAPI paths with operations, parameters, and security
• Type System: Intelligent type parsing that converts Mastodon documentation types to OpenAPI types (String → string, Integer → integer, Boolean → boolean, etc.)
• Parameter Handling: Supports both path parameters and form data parameters with proper OpenAPI structure
• Security Integration: Automatically adds OAuth2 security requirements based on method documentation

Usage

npm run generate

This now outputs a complete OpenAPI JSON specification instead of console logging the parsed data.

Output Structure

The generated schema includes:

• OpenAPI 3.0.3 specification with proper info and servers
• 64 entity schemas in components.schemas
• 144 API paths with complete operation definitions
• OAuth2 and Bearer token security schemes
• Proper parameter handling for both query and form data

Testing

Added comprehensive test coverage for the OpenAPI generator including:

• Entity to schema conversion validation
• API method to path operation conversion
• Type parsing and mapping
• JSON output validation

Fixes #18.

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