Migrations and Helpers API flexibility improvements and documentation

[harrisonde]

✨ Add documentation and improve API flexibility for migrations and helpers

📝 Summary

• Added comprehensive GoDoc comments with usage examples to database/migrations and helpers packages
• Made maxBytes parameter optional in ReadJSON with a sensible default of 1MB

🔧 Changes

database/migrations/migrate.go

• 📚 Added package-level documentation
• 📚 Added GoDoc comments to MigrateUp, MigrateDownAll, Steps, and MigrateForce

database/migrations/pop.go

• 📚 Added GoDoc comments to PopConnect, CreatePopMigration, RunPopMigrations, PopMigrateDown, and PopMigrateReset
• 📚 Documented parameter details for CreatePopMigration

helpers/response-utils.go

• 📚 Added GoDoc comments with practical code examples for all methods
• 🚀 Made maxBytes an optional variadic parameter in ReadJSON (defaults to 1048576 bytes / 1MB)
• ✅ Backward compatible - existing code continues to work without changes

💡 Example Usage (new optional parameter)

// Use default 1MB limit
err := helpers.ReadJSON(w, r, &data)

// Or specify custom limit (512KB)
err := helpers.ReadJSON(w, r, &data, 524288)