MasterKeyFromEnv creates a new instance of a local secret lock Reader to read a master key found in a env variable with key: `envPrefix` + `keyURI`.

MasterKeyFromPath creates a new instance of a local secret lock Reader to read a master key stored in `path`.

NewService creates a new instance of local secret lock service using a master key in masterKeyReader.

Lock is a secret lock service responsible for encrypting keys using a master key.