With this change, the location of the secret SSH key can be configured
through `${RAD_HOME}/config.json` so that the node key does not have to
be placed under `${RAD_HOME}/keys` anymore.
Further, there is now an option to override `config.json` directly when
executing `radicle-node` via the command line argument
`--secret`.
The primary motivation is more flexible deployments, for example
leveraging external secret management solutions, like
<https://systemd.io/CREDENTIALS/>.
The secret key is fingerprinted by taking the fingerprint of the public
key corresponding to the secret key. This allows to detect when the
secret key changes.
While running `cargo-semver-checks`, there was an issue that was surfaced
regarding `serde(into)`, `serde(try_from)` and `schemars(transparent)` being
used, and they are incompatible.
This appeared to be a semver issue, on the side of `schemars`, since the issue
would only appear when adding `radicle` as a fresh dependency. The intuition for
this is that once `schemars` was updated locally, the same error appeared when
attempting to build the `radicle` crate.
To avoid this, `schemars` provides a `!` operator for the macro[^0]:
> You can also “unset” serde attributes by including them with a ! prefix in a
> schemars attribute, which will make schemars ignore the corresponding serde
> attribute item
[^0]: https://docs.rs/schemars_derive/latest/schemars_derive/derive.JsonSchema.html#attributes