Integrating go-fed into Gitea

@techknowlogick I think the implementation is ready for review. Now comes the delicate part (because I do not have a GitHub account). Would you mind copy/pasting it on my behalf and create a pull request from it? Don’t hesitate to tell me if this is too much right now and I’ll ask someone else.

  • Commits: git clone -b wip-go-fed
  • Title: activitypub: implement /api/v1/activitypub/user/{username}
  • Description:
These two commits:

* add [go-fed]( as a dependency of Gitea: it is a requirement to move forward with [federation]( 
* implement the **/api/v1/activitypub/user/{username}** endpoint which:
  * verifies the username matches an existing Gitea user;
  * creates an ActivityStream [Person]( using the [ActivityStreamsPerson]( object provided by go-fed;
  * sets the [Actor required fields]( (inbox, outbox) and the [Object required field]( (id). The type of the object is already set by go-fed.

It includes integration tests that verify the ActivityPub message can be decoded (using go-fed) on the receiving end.

Discussion topics:

* [Adding go-fed as a dependency to Gitea](
* [Integrating go-fed into Gitea](