References: - https://blog.joinmastodon.org/2018/06/how-to-implement-a-basic-activitypub-server/ - https://swicg.github.io/activitypub-http-signature/#how-to-obtain-a-signature-s-public-key - https://shkspr.mobi/blog/2024/02/activitypub-server-in-a-single-file/
