disk: new interface UniqueEntity for Entities with UUID

This is for all entities that have a uniquely identifiable via a UUID.
Currently the interface only contains a single function, GenUUID(),
that should generate a new UUID via a random source (`rand.Rand`).
NB: Partitions are uniquely identifiable if and only if the layout is
GPT.

Co-Authored-By: Achilleas Koutsou <achilleas@koutsou.net>

internal/disk/disk.go

@@ -19,6 +19,7 @@ package disk
 import (
 	"encoding/hex"
 	"io"
+	"math/rand"
 
 	"github.com/google/uuid"
 )
@@ -102,6 +103,14 @@ type VolumeContainer interface {
 	CreateVolume(mountpoint string, size uint64) (Entity, error)
 }
 
+// A UniqueEntity is an entity that can be uniquely identified via a UUID.
+//
+// GenUUID generates a UUID for the entity if it does not yet have one.
+type UniqueEntity interface {
+	Entity
+	GenUUID(rng *rand.Rand)
+}
+
 // FSSpec for a filesystem (UUID and Label); the first field of fstab(5)
 type FSSpec struct {
 	UUID  string