feat: Implement offline gateway

[dariusc93]

What this PR does 📖

• Implements external gateway for identity discovery and basic routing
• Exports and restore account and friends list.

Which issue(s) this PR fixes 🔨

• Relates to Restore Account, Friends, et al #43
• Resolves Offline Friend Request #44

Special notes for reviewers 🗒️

• This does not support offline message routing or files at this time but only exporting and importing the account from a remote gateway and basic routing of request.

Additional comments 🎤

• This gateway, codename shuttle, is a protocol and service which succeeds add: Implemented tools #262 (see https://github.com/Satellite-im/Warp/blob/warp/tools/tools/shuttle/README.md on the original design, which is meant to work based on how the extensions were prior to Merge warp-*-ipfs crates #222) in handling offline support and discovery, including some basic request routing.