Add ed25519 signing

[Reasonable-Solutions]

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Use Cases

use case:
When ingesting or transforming security related events it is often good and cool to have
chain of custody and tamper evidence. This is also neat to have when discussing compliance and audit trails.
This can be achieved by signing the data at each step or service

Attempted Solutions

No response

Proposal

I'm thinking something like

.signature = ed25519_sign!(.data, key: "/path/to/private.key") 

and with the implementation being basically wrapping dalek primitives

fn ed25519_sign(data: Value, key_path) -> Result<Value> {
.. steps  
  Ok(base64::encode(signature.to_bytes()).into())
}

References

No response