Jiwon Kwon

## Summary This PR refactors the `@fedify/relay` package to introduce a factory pattern that supports multiple relay implementations, specifically **Mastodon** and **LitePub** relay protocols. The changes improve code organization, maintainability,...

There are multiple ways to reduce the duplicated codes: 1) To separate that patterns and have 3 functions (`render(), renderRequest(), renderResponse()`) 2) To combine two functions and have if conditions...