feat(tx): run update re-fetch and post-commit hooks in a second transaction

Re-fetch, BeforeScan and AfterUpdate/AfterCreate now run on a short
transaction that fires OnTxBegin. Existence selects inside the first
transaction use tx instead of the pool.

pkg/resolvespec/update_tx_test.go

@@ -0,0 +1,48 @@
+package resolvespec
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"github.com/DATA-DOG/go-sqlmock"
+
+	"github.com/bitechdev/ResolveSpec/pkg/common"
+)
+
+func TestUpdateRefetchRunsInSecondTransaction(t *testing.T) {
+	h, mock, _ := newDeleteHarness(t)
+	var begins []common.Database
+	h.Hooks().Register(OnTxBegin, func(ctx *HookContext) error {
+		begins = append(begins, ctx.Tx)
+		return nil
+	})
+
+	cols := []string{"id", "name"}
+	mock.ExpectBegin()
+	mock.ExpectQuery(`SELECT`).WillReturnRows(sqlmock.NewRows(cols).AddRow(7, "a"))
+	mock.ExpectExec(`UPDATE`).WillReturnResult(sqlmock.NewResult(0, 1))
+	mock.ExpectCommit()
+	mock.ExpectBegin()
+	mock.ExpectQuery(`SELECT`).WillReturnRows(sqlmock.NewRows(cols).AddRow(7, "b"))
+	mock.ExpectCommit()
+
+	rec := httptest.NewRecorder()
+	w, _ := common.WrapHTTPRequest(rec, httptest.NewRequest(http.MethodPut, "/", nil))
+	base, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+	defer cancel()
+	ctx := WithRequestData(base, "public", "items", "items", &delItem{}, &delItem{})
+	h.handleUpdate(ctx, w, "7", nil, map[string]interface{}{"name": "b"}, common.RequestOptions{})
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status %d body %s", rec.Code, rec.Body)
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Fatal(err)
+	}
+	if len(begins) != 2 || begins[0] == begins[1] {
+		t.Fatalf("OnTxBegin must fire once per transaction (2), got %d", len(begins))
+	}
+}