QSS: Update Quiet to connect to server when joining community

[leblowl]

For the initial implementation, the invite data on the server can provide the information required for a peer to connect to the network, but it doesn't need to provide message history or channels.

As a very basic implementation, we could do something like the following. When joining via a v2 invite link, the user calls a new DOWNLOAD_INVITE_DATA endpoint where the backend fetches the invite data from the server and returns it to the user. The backend can fetch the invite data from the server using purely NodeJS to start with. Once, the invite data is returned to the user, the user continues as they normally do to connect to the network by calling CREATE_NETWORK/LAUNCH_COMMUNITY.

[EmiM]

#2393

Due to delay in our sprint schedules this step became a part of the next step (#2312) so it will be merged as one MR:
#2438