Link device in JSON-RPC mode

[kxait]

Hi, there was an update to signal-cli regarding linking devices in JSON-RPC mode, it would be really nice to have this support in this project, as for e.g. my application I need to be able to link devices on the fly.
Issue: AsamK/signal-cli#1319
Commit: AsamK/signal-cli@a7a5947
It requires the json-rpc client to be connected without a -u parameter (in multi-account mode), and for there to be 2 requests sent (startLink which gets the QR code and finishLink which waits for the device to be registered). It seems this would require big changes in the way we handle the JSON-RPC connections

1. Do not assume every json-rpc connection needs a phone number associated with it
2. Add a multi-account mkfifo to signal-cli

• do not crash if we didn't find any registered numbers at the beginning?

3. Send a request after we return the QR code and wait for it to finish or wait for a timeout
4. Regenerate the jsonrpc2.yml config after the linking is finished and reload it

So far, I have got it to actually link the number in the background and add it to data/, but I think actually reloading jsonrpc2.yml would require some big changes and assistance/guidance from @bbernhard (let me know if I'm on the right path)

My branch: c7f2283

[GIN] 2023/10/29 - 10:47:31 | 200 |  1.531793584s |      172.17.0.1 | GET      "/v1/qrcodelink?device_name=test"
2023/10/29 10:47:46 Linking device result: {"number":"+48123456789"}

[kxait]

moved to issue #433 as I think it's a better fit there