[8] delegated signing to third-party server

[nikhilsaraf]

Desired Behavior

I want to add the ability to only place my public key in Kelp and have my secret key on a third party server for security purposes

Impact

The desired behavior will allow me to deploy my kelp bot on a public cloud while controlling signatures from a protected environment such as my private server or something like fireblocks.

Feature Suggestion

We can achieve the desired behavior by using SEP-0007 to delegate the signature request from Kelp

This should only modify the trader file. Issue #711 will add support for delegated signing in the Kelp GUI

You can also add a command-line argument called --delegated-signing-url that passes in a delegated signing URL to use for the kelp trade command (overriding anything set in the trader.cfg file). This will make it easier for the Kelp GUI to pass the delegated signing URL to the Kelp GUI bots when started (without having to constantly modify each trader.cfg file before it is run).