Migratior up function throws error when running on Bun

[danlannz]

When running migratior.up() on bun I'm getting migration error as MigrationClass is undefined.

MigrationError: Migration Migration20240318042632 (up) failed: Original error: undefined is not a constructor (evaluating 'new (Object.values(migration))[0](this.driver, this.config)')
 info: {
  "direction": "up",
  "name": "Migration20240318042632",
  "path": "/mikro-orm-elysia/src/migrations/Migration20240318042632.ts",
  "context": {}
}

      at new ErrorWithCause (/mikro-orm-elysia/node_modules/pony-cause/lib/error-with-cause.js:4:12)
      at new MigrationError (/mikro-orm-elysia/node_modules/umzug/lib/umzug.js:45:9)
      at /mikro-orm-elysia/node_modules/umzug/lib/umzug.js:177:31

196 |     }
197 |     resolve(params) {
198 |         const createMigrationHandler = async (method) => {
199 |             const migration = await core_1.Utils.dynamicImport(params.path);
200 |             const MigrationClass = Object.values(migration)[0];
201 |             const instance = new MigrationClass(this.driver, this.config);
                                                       ^
TypeError: undefined is not a constructor (evaluating 'new (Object.values(migration))[0](this.driver, this.config)')
      at /mikro-orm-elysia/node_modules/@mikro-orm/migrations/Migrator.js:201:50

Doing some debugging it appears that the Object.values returns an empty array from the dynamic import object on Bun

mikro-orm/packages/migrations/src/Migrator.ts

Lines 250 to 251 in 8799461

	const migration = await Utils.dynamicImport(params.path!);
	const MigrationClass = Object.values(migration)[0] as Constructor<Migration>;

I'm currently using the following workaround, will open a PR if this workaround is also compatible with all supported runtimes

  const migration = await Utils.dynamicImport(params.path!); 
  const fileName = params.name.split('.')[0];
  const MigrationClass = migration[fileName];