Chat Federation: using S2S if available.

* if both local and remote instance have external XMPP connections enabled, the user joins the remote room with his local account
* some code refactoring (builtin.ts)

Note: documentation and settings descriptions are to do.

Related to #112

server/lib/federation/connection-infos.ts

@@ -31,6 +31,17 @@ function anonymousConnectionInfos (livechatInfos: LiveChatJSONLDAttribute | fals
   return r
 }
 
-export {
-  anonymousConnectionInfos
+function remoteAuthenticatedConnectionEnabled (livechatInfos: LiveChatJSONLDAttribute | false): boolean {
+  if (!livechatInfos) { return false }
+  if (!livechatInfos.links) { return false }
+  if (livechatInfos.type !== 'xmpp') { return false }
+  for (const link of livechatInfos.links) {
+    if (link.type === 'xmpp-s2s') { return true }
+  }
+  return false
+}
+
+export {
+  anonymousConnectionInfos,
+  remoteAuthenticatedConnectionEnabled
 }

server/lib/federation/outgoing.ts

@@ -31,7 +31,8 @@ async function videoBuildJSONLD (
     'disable-websocket',
     'prosody-room-type',
     'federation-dont-publish-remotely',
-    'chat-no-anonymous'
+    'chat-no-anonymous',
+    'prosody-room-allow-s2s'
   ])
 
   if (settings['federation-dont-publish-remotely']) {
@@ -70,6 +71,11 @@ async function videoBuildJSONLD (
   }
 
   const links: LiveChatJSONLDLink[] = []
+  if (settings['prosody-room-allow-s2s']) {
+    links.push({
+      type: 'xmpp-s2s'
+    })
+  }
   if (!settings['chat-no-anonymous']) {
     links.push({
       type: 'xmpp-bosh-anonymous',

server/lib/federation/sanitize.ts

@@ -36,6 +36,11 @@ function sanitizePeertubeLiveChatInfos (chatInfos: any): LiveChatJSONLDAttribute
         url: link.url
       })
     }
+    if (link.type === 'xmpp-s2s') {
+      r.links.push({
+        type: link.type
+      })
+    }
   }
   return r
 }

server/lib/federation/types.ts

@@ -4,6 +4,10 @@ interface VideoBuildResultContext {
   video: MVideoAP
 }
 
+interface LiveChatJSONLDS2SLink {
+  type: 'xmpp-s2s'
+}
+
 interface LiveChatJSONLDAnonymousWebsocketLink {
   type: 'xmpp-websocket-anonymous'
   url: string
@@ -16,7 +20,7 @@ interface LiveChatJSONLDAnonymousBOSHLink {
   jid: string
 }
 
-type LiveChatJSONLDLink = LiveChatJSONLDAnonymousBOSHLink | LiveChatJSONLDAnonymousWebsocketLink
+type LiveChatJSONLDLink = LiveChatJSONLDS2SLink | LiveChatJSONLDAnonymousBOSHLink | LiveChatJSONLDAnonymousWebsocketLink
 
 interface LiveChatJSONLDInfos {
   type: 'xmpp'