fix: sqlserver_beta (#33)

## Description

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relates to #1234

## Checklist

- [ ] Issue was linked above
- [ ] Code format was applied: `make fmt`
- [ ] Examples were added / adjusted (see `examples/` directory)
- [x] Docs are up-to-date: `make generate-docs` (will be checked by CI)
- [ ] Unit tests got implemented or updated
- [ ] Acceptance tests got implemented or updated (see e.g. [here](f5f99d1709/stackit/internal/services/dns/dns_acc_test.go))
- [x] Unit tests are passing: `make test` (will be checked by CI)
- [x] No linter issues: `make lint` (will be checked by CI)

Reviewed-on: #33
Reviewed-by: Andre_Harms <andre.harms@stackit.cloud>
Co-authored-by: Marcel S. Henselin <marcel.henselin@stackit.cloud>
Co-committed-by: Marcel S. Henselin <marcel.henselin@stackit.cloud>

stackit/internal/wait/sqlserverflexalpha/wait.go

@@ -32,6 +32,11 @@ type APIClientInstanceInterface interface {
 	GetInstanceRequestExecute(ctx context.Context, projectId, region, instanceId string) (*sqlserverflex.GetInstanceResponse, error)
 }
 
+// APIClientUserInterface Interface needed for tests
+type APIClientUserInterface interface {
+	DeleteUserRequestExecute(ctx context.Context, projectId string, region string, instanceId string, userId int64) error
+}
+
 // CreateInstanceWaitHandler will wait for instance creation
 func CreateInstanceWaitHandler(ctx context.Context, a APIClientInstanceInterface, projectId, instanceId, region string) *wait.AsyncActionHandler[sqlserverflex.GetInstanceResponse] {
 	handler := wait.New(func() (waitFinished bool, response *sqlserverflex.GetInstanceResponse, err error) {
@@ -131,3 +136,36 @@ func DeleteInstanceWaitHandler(ctx context.Context, a APIClientInstanceInterface
 	handler.SetTimeout(15 * time.Minute)
 	return handler
 }
+
+// DeleteUserWaitHandler will wait for instance deletion
+func DeleteUserWaitHandler(
+	ctx context.Context,
+	a APIClientUserInterface,
+	projectId, instanceId, region string,
+	userId int64,
+) *wait.AsyncActionHandler[struct{}] {
+	handler := wait.New(func() (waitFinished bool, response *struct{}, err error) {
+		err = a.DeleteUserRequestExecute(ctx, projectId, region, instanceId, userId)
+		if err == nil {
+			return false, nil, nil
+		}
+		var oapiErr *oapierror.GenericOpenAPIError
+		ok := errors.As(err, &oapiErr)
+		if !ok {
+			return false, nil, fmt.Errorf("could not convert error to oapierror.GenericOpenAPIError")
+		}
+
+		switch oapiErr.StatusCode {
+		case http.StatusNotFound:
+			return true, nil, nil
+		case http.StatusInternalServerError:
+			tflog.Warn(ctx, "Wait handler got error 500")
+			return false, nil, nil
+		default:
+			return false, nil, err
+		}
+	})
+	handler.SetTimeout(15 * time.Minute)
+	handler.SetSleepBeforeWait(15 * time.Second)
+	return handler
+}