ActivityPubでのプロポーザルと実装例がこちらになりますの
fep/fep/2c59/fep-2c59.md at main - fediverse/fep - Codeberg.org
https://codeberg.org/fediverse/fep/src/branch/main/fep/2c59/fep-2c59.md
FEP-2c59, add "webfinger" to user actor (!4099) · Merge requests · Pleroma / pleroma · GitLab
https://git.pleroma.social/pleroma/pleroma/-/merge_requests/4099