Add federation back (#15283)

app/federation/client/admin/dashboard.html

app/federation/client/admin/dashboard.js

app/federation/client/index.js

app/federation/client/messageTypes.js

app/federation/server/PeerClient.js

app/federation/server/PeerDNS.js

app/federation/server/PeerHTTP/PeerHTTP.js

app/federation/server/PeerHTTP/index.js

app/federation/server/PeerHTTP/utils.js

app/federation/server/PeerPinger.js

app/federation/server/PeerServer/PeerServer.js

app/federation/server/PeerServer/index.js

app/federation/server/PeerServer/routes/events.js

app/federation/server/PeerServer/routes/users.js

app/federation/server/config.js

app/federation/server/endpoints/dispatch.js

app/federation/server/endpoints/index.js

app/federation/server/endpoints/requestFromLatest.js

app/federation/server/endpoints/uploads.js

app/federation/server/endpoints/users.js