fix: protect method names from token registration collisions

[baima365-web]

Problem

Calling morgan.token('token', fn) overwrites the morgan.token() method itself, breaking all subsequent token registrations. This is because morgan serves as both the module export (with methods token, format, compile) and the token registry.

Example:

var logger = require('morgan');
logger.token('token', function (req, res) { return 'value' });
// morgan.token is now the custom function, not the registration method
logger.token('uuid', function (req, res) { return 'uuid' }); // TypeError: tokens.uuid is not a function

Fix

Make the token, format, and compile methods non-writable using Object.defineProperties. This prevents user token registrations from overwriting the module API while maintaining full backward compatibility.

Test plan

• Existing built-in tokens work correctly
• Custom token registration works
• Compiled format functions resolve tokens correctly
• Middleware logs correctly
• Registering reserved names (token, format, compile) now throws instead of silently breaking