feat: add schema user create and remove (#8494)

# Which Problems Are Solved

Added functionality that user with a userschema can be created and
removed.

# How the Problems Are Solved

Added logic and moved APIs so that everything is API v3 conform.

# Additional Changes

- move of user and userschema API to resources folder
- changed testing and parameters
- some renaming

# Additional Context

closes #7308

---------

Co-authored-by: Elio Bischof <elio@zitadel.com>

internal/api/grpc/resources/userschema/v3alpha/server_integration_test.go

@@ -0,0 +1,71 @@
+//go:build integration
+
+package userschema_test
+
+import (
+	"context"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/muhlemmer/gu"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/zitadel/zitadel/internal/integration"
+	"github.com/zitadel/zitadel/pkg/grpc/feature/v2"
+	schema "github.com/zitadel/zitadel/pkg/grpc/resources/userschema/v3alpha"
+)
+
+var (
+	IAMOwnerCTX, SystemCTX context.Context
+	Tester                 *integration.Tester
+	Client                 schema.ZITADELUserSchemasClient
+)
+
+func TestMain(m *testing.M) {
+	os.Exit(func() int {
+		ctx, _, cancel := integration.Contexts(5 * time.Minute)
+		defer cancel()
+
+		Tester = integration.NewTester(ctx)
+		defer Tester.Done()
+
+		IAMOwnerCTX = Tester.WithAuthorization(ctx, integration.IAMOwner)
+		SystemCTX = Tester.WithAuthorization(ctx, integration.SystemUser)
+		Client = Tester.Client.UserSchemaV3
+
+		return m.Run()
+	}())
+}
+
+func ensureFeatureEnabled(t *testing.T, iamOwnerCTX context.Context) {
+	f, err := Tester.Client.FeatureV2.GetInstanceFeatures(iamOwnerCTX, &feature.GetInstanceFeaturesRequest{
+		Inheritance: true,
+	})
+	require.NoError(t, err)
+	if f.UserSchema.GetEnabled() {
+		return
+	}
+	_, err = Tester.Client.FeatureV2.SetInstanceFeatures(iamOwnerCTX, &feature.SetInstanceFeaturesRequest{
+		UserSchema: gu.Ptr(true),
+	})
+	require.NoError(t, err)
+	retryDuration := time.Minute
+	if ctxDeadline, ok := iamOwnerCTX.Deadline(); ok {
+		retryDuration = time.Until(ctxDeadline)
+	}
+	require.EventuallyWithT(t,
+		func(ttt *assert.CollectT) {
+			f, err := Tester.Client.FeatureV2.GetInstanceFeatures(iamOwnerCTX, &feature.GetInstanceFeaturesRequest{
+				Inheritance: true,
+			})
+			require.NoError(ttt, err)
+			if f.UserSchema.GetEnabled() {
+				return
+			}
+		},
+		retryDuration,
+		100*time.Millisecond,
+		"timed out waiting for ensuring instance feature")
+}