fix: multiple setup steps (#773)

* fix: multiple setup steps

* fix: test set up started

* fix: possible nil pointers in setup

* fix: validate executed step

internal/setup/step.go

@@ -0,0 +1,14 @@
+package setup
+
+import (
+	"context"
+
+	iam_model "github.com/caos/zitadel/internal/iam/model"
+)
+
+type step interface {
+	step() iam_model.Step
+	execute(context.Context) error
+	init(*Setup)
+	isNil() bool
+}