feat: action v2 signing (#8779)

# Which Problems Are Solved

The action v2 messages were didn't contain anything providing security
for the sent content.

# How the Problems Are Solved

Each Target now has a SigningKey, which can also be newly generated
through the API and returned at creation and through the Get-Endpoints.
There is now a HTTP header "Zitadel-Signature", which is generated with
the SigningKey and Payload, and also contains a timestamp to check with
a tolerance if the message took to long to sent.

# Additional Changes

The functionality to create and check the signature is provided in the
pkg/actions package, and can be reused in the SDK.

# Additional Context

Closes #7924

---------

Co-authored-by: Livio Spring <livio.a@gmail.com>

internal/command/action_v2_target_model_test.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/stretchr/testify/assert"
 
+	"github.com/zitadel/zitadel/internal/crypto"
 	"github.com/zitadel/zitadel/internal/domain"
 	"github.com/zitadel/zitadel/internal/eventstore"
 	"github.com/zitadel/zitadel/internal/repository/target"
@@ -20,6 +21,12 @@ func targetAddEvent(aggID, resourceOwner string) *target.AddedEvent {
 		"https://example.com",
 		time.Second,
 		false,
+		&crypto.CryptoValue{
+			CryptoType: crypto.TypeEncryption,
+			Algorithm:  "enc",
+			KeyID:      "id",
+			Crypted:    []byte("12345678"),
+		},
 	)
 }