fix: improve initialization of custom repository

[parly]

Description of change

This patch fixes initialization of the custom repository. Without this patch, the following queries were not being executed within a transaction.

await dataSource.transaction(async (manager) => {
  const customRepository = manager.withRepository(CustomRepository);
  const data = await customRepository.find({/* ... */});
});

Pull-Request Checklist

• Code is up-to-date with the master branch
• npm run format to apply prettier formatting
• npm run test passes with this change
• This pull request links relevant issues as Fixes #0000
• There are new or updated unit tests validating the change
• Documentation has been updated to reflect this change
• The new commits follow conventions explained in CONTRIBUTING.md

[pleerock]

thank you!