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.go

@@ -0,0 +1,65 @@
+package userschema
+
+import (
+	"context"
+
+	"google.golang.org/grpc"
+
+	"github.com/zitadel/zitadel/internal/api/authz"
+	"github.com/zitadel/zitadel/internal/api/grpc/server"
+	"github.com/zitadel/zitadel/internal/command"
+	"github.com/zitadel/zitadel/internal/config/systemdefaults"
+	"github.com/zitadel/zitadel/internal/query"
+	"github.com/zitadel/zitadel/internal/zerrors"
+	schema "github.com/zitadel/zitadel/pkg/grpc/resources/userschema/v3alpha"
+)
+
+var _ schema.ZITADELUserSchemasServer = (*Server)(nil)
+
+type Server struct {
+	schema.UnimplementedZITADELUserSchemasServer
+	systemDefaults systemdefaults.SystemDefaults
+	command        *command.Commands
+	query          *query.Queries
+}
+
+type Config struct{}
+
+func CreateServer(
+	systemDefaults systemdefaults.SystemDefaults,
+	command *command.Commands,
+	query *query.Queries,
+) *Server {
+	return &Server{
+		systemDefaults: systemDefaults,
+		command:        command,
+		query:          query,
+	}
+}
+
+func (s *Server) RegisterServer(grpcServer *grpc.Server) {
+	schema.RegisterZITADELUserSchemasServer(grpcServer, s)
+}
+
+func (s *Server) AppName() string {
+	return schema.ZITADELUserSchemas_ServiceDesc.ServiceName
+}
+
+func (s *Server) MethodPrefix() string {
+	return schema.ZITADELUserSchemas_ServiceDesc.ServiceName
+}
+
+func (s *Server) AuthMethods() authz.MethodMapping {
+	return schema.ZITADELUserSchemas_AuthMethods
+}
+
+func (s *Server) RegisterGateway() server.RegisterGatewayFunc {
+	return schema.RegisterZITADELUserSchemasHandler
+}
+
+func checkUserSchemaEnabled(ctx context.Context) error {
+	if authz.GetInstance(ctx).Features().UserSchema {
+		return nil
+	}
+	return zerrors.ThrowPreconditionFailed(nil, "SCHEMA-SFjk3", "Errors.UserSchema.NotEnabled")
+}