* feat: Exposes a hook to mod_external_services data.

The hook can be used to get turn servers and credentials from another module.

* feat: JiConOp2 pushes a message with some info to clients.

* feat: JiConOp adds config for shard name feature.

* squash: Changes message type to service-info.

* squash: Drops the event in external_services.

* feat: Uses mod_external_services supporting urn:xmpp:extdisco:2.

The old mod_turncredentials.lua is left to continue working for those using old installs.
New install will start using the new module which will no longer be needed with prosody 0.12.

https://hg.prosody.im/prosody-modules/file/4841cf3fded5/mod_external_services/mod_external_services.lua

* squash: Updates ljm to support urn:xmpp:extdisco:2.