I'm working on exactly that: a service that acts as an ActivityPub server (code[1], example[2], example application running on top of it[3]) for users in the form of a static binary. It supports multiple storage backends that can be selected individually or all together at build time and it can be extended to many more.
[1] https://github.com/go-ap/fedbox
[3] https://littr.me
What we need is an AP store, and then applications build on top of it, like your project does. But at this point I question whether matrix wouldn't be a better platform
Basically, the domain has much more significance than it really needs
Aside from a job-search bot, I haven't written many software, and it looks like what you are working on might actually be a very solid foundation. It's a pity my go isn't that established (rust and ruby here) but certainly will consider this going forward. Huddling around common base libraries is also certainly something the fediverse needs, rather than re-building AP again in "language X".
[1] The hardest part has proven to be the fact that "linkedin" is an entirely different product depending on who you ask. It solves entirely different solutions, depending on who you ask. And it has entirely different features, depending on who you ask. Turns out LinkedIn is quite hard to "copy", "port" or even define for the fediverse. Aside from that this makes it a giant task to do. Is it a place to find jobs? To recruit? To keep in touch with colleagues? To connect with other entrepeneurs? To spam lame motivational quotes? To pitch your book or a Rolodex-on-steroids? Its all of that and more.
There is talk at the moment about adding federation to got forges: let instances talk together, accounts cross post, etc. It's centered around instances and they have specific addons to interact. Matrix can make it work because it takes a radically orthogonal approach: rooms are front and center. Rooms can be joined by anyone anywhere. Rooms are replicated. The homeserver is a technical detail in service of the functional source of truth: the Room, an append-only log of arbitrary json. There is also a key-value store for arbitrary blobs to store binary stuff.
In the context of forges, a repo can be a room: events for issues/replies, events for merge requests, events for CI/CD blobs for actual code storage and releases, ... Anyone can join and push events, with the correct rights of course, so you have branches included. Everything is replicated. No one cares what instance you are from.
I seriously invite you to consider the semantically model of Matrix, it's pretty good.
