The data part of the add history request is actually a string. I don't
want to introduce any structure here, and would rather keep it as "just
a blob". Even if that blob has structure secretly!
My fault for missing this in the last review
* Switch to Cargo workspaces
Breaking things into "client", "server" and "common" makes managing the
codebase much easier!
client - anything running on a user's machine for adding history
server - handles storing/syncing history and running a HTTP server
common - request/response API definitions, common utils, etc
* Update dockerfile
