mastodon/app/controllers/activitypub/follows_controller.rb

# frozen_string_literal: true

class ActivityPub::FollowsController < Api::BaseController
  include SignatureVerification

  def show
    render(
      json: FollowRequest.includes(:account).references(:account).find_by!(
        id: params.require(:id),
        accounts: { domain: nil, username: params.require(:account_username) },
        target_account: signed_request_account
      ),
      serializer: ActivityPub::FollowSerializer,
      adapter: ActivityPub::Adapter,
      content_type: 'application/activity+json'
    )
  end
end