chore: move the go code into a subfolder

apps/api/internal/domain/instance_domain.go

@@ -0,0 +1,38 @@
+package domain
+
+import (
+	"strings"
+
+	"github.com/zitadel/zitadel/internal/crypto"
+)
+
+var (
+	domainRunes = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")
+)
+
+type InstanceDomainState int32
+
+const (
+	InstanceDomainStateUnspecified InstanceDomainState = iota
+	InstanceDomainStateActive
+	InstanceDomainStateRemoved
+
+	instanceDomainStateCount
+)
+
+func (f InstanceDomainState) Valid() bool {
+	return f >= 0 && f < instanceDomainStateCount
+}
+
+func (f InstanceDomainState) Exists() bool {
+	return f == InstanceDomainStateActive
+}
+
+func NewGeneratedInstanceDomain(instanceName, iamDomain string) (string, error) {
+	randomString, err := crypto.GenerateRandomString(6, domainRunes)
+	if err != nil {
+		return "", err
+	}
+	instanceName = strings.TrimSpace(instanceName)
+	return strings.ToLower(strings.ReplaceAll(instanceName, " ", "-") + "-" + randomString + "." + iamDomain), nil
+}