disk: new type LUKSContainer

Representation for the encrypted storage container of the same name.

Implements the following disk interfaces:
- Entity
- Container

Co-Authored-By: Christian Kellner <christian@kellner.me>

internal/disk/luks.go

@@ -0,0 +1,40 @@
+package disk
+
+import "fmt"
+
+type Argon2id struct {
+	Iterations  uint
+	Memory      uint
+	Parallelism uint
+}
+type LUKSContainer struct {
+	Passphrase string
+	UUID       string
+	Cipher     string
+	Label      string
+	Subsystem  string
+	SectorSize uint64
+
+	// password-based key derivation function
+	PBKDF Argon2id
+
+	Payload Entity
+}
+
+func (lc *LUKSContainer) IsContainer() bool {
+	return true
+}
+
+func (lc *LUKSContainer) GetItemCount() uint {
+	if lc.Payload == nil {
+		return 0
+	}
+	return 1
+}
+
+func (lc *LUKSContainer) GetChild(n uint) Entity {
+	if n != 0 {
+		panic(fmt.Sprintf("invalid child index for LUKSContainer: %d != 0", n))
+	}
+	return lc.Payload
+}