HTTP endpoint to return key information

Motivation

We need policy extension function to retrieve keys from Vault or OCM. Instead of making the policies communicate directly with Vault or OCM for keys, they will ask the signer service for this information.

Details

Request:

GET /v1/keys/{keyname}

Response:

{
  "name":"key1",
  "type":"ed25519",
  "public_key":"..."
}