Add Go CSV parser implementation with jsonic plugin

[rjrodger]

Summary

This PR adds a complete CSV parser implementation for Go with support for the jsonic plugin system. The implementation provides RFC 4180-compliant CSV parsing with extensive configuration options and a comprehensive test suite.

Key Changes

Core Parser Implementation (go/csv.go)

• Implements Parse() function for parsing CSV text with configurable options
• Supports RFC 4180 quoted field handling with double-quote escaping
• Configurable field and record separators (default: comma and newline)
• Optional value transformations:
  • Whitespace trimming
  • Number parsing (integers and floats)
  • Boolean/null keyword recognition
  • Comment line support (lines starting with #)
• Streaming callback support for processing records as they're parsed
• Maintains field order through orderedMap type for consistent JSON comparison

Plugin Integration (go/plugin.go)

• Csv plugin function for jsonic integration with high-priority matcher
• MakeJsonic() factory function for creating pre-configured jsonic instances
• mapToOptions() helper to convert plugin configuration maps to CsvOptions
• Automatic normalization of internal types for jsonic compatibility

Configuration Options

• CsvOptions: Main configuration struct with boolean pointers for optional settings
• FieldOptions: Field-level configuration (separator, naming, empty field handling)
• RecordOptions: Record-level configuration (custom separators, empty record preservation)
• Strict mode (default true) that disables automatic transformations; non-strict mode enables trim/comment/number by default

Test Suite (go/csv_test.go)

• Fixture-based testing framework loading test cases from test/fixtures/manifest.json
• 20+ test fixtures covering:
  • Basic CSV parsing with headers
  • Array vs object output formats
  • Quoted fields with embedded newlines and escaped quotes
  • Custom field and record separators
  • Comment handling (line and inline)
  • Value transformations (trim, number, boolean/null parsing)
  • Empty record handling
  • CRLF and various line ending formats
• Unit tests for plugin interfaces and streaming callbacks
• Helper functions for test assertions and value normalization

Test Fixtures

• CSV test files with corresponding expected JSON output
• Manifest configuration defining test parameters and options
• Coverage of edge cases: empty fields, trailing newlines, leading newlines, multi-character separators

Build Configuration

• Go module definition (go/go.mod) with jsonic dependency

Notable Implementation Details

• Parser State Machine: Uses position-based parsing with lookahead for separator detection
• Quote Handling: Implements RFC 4180 double-quote escaping ("" → ")
• Flexible Separators: Supports multi-character field and record separators
• Ordered Maps: Preserves field insertion order for deterministic JSON output in tests
• Streaming Support: Optional callback interface for processing records without buffering entire result
• Strict vs Non-Strict Modes: Allows different default behaviors for transformation options
• Empty Record Handling: Distinguishes between truly empty records and records with empty fields

https://claude.ai/code/session_01Ehie1ims4jJtda9A6MmD1x