fix: replace err.Error() string match with errors.Is(err, pgx.ErrTxClosed)

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/handlers/admin/custom_services.go

@@ -395,7 +395,7 @@ func UpdateCustomService(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	defer func() {
-		if err := tx.Rollback(r.Context()); err != nil && err.Error() != "tx is closed" {
+		if err := tx.Rollback(r.Context()); err != nil && !errors.Is(err, pgx.ErrTxClosed) {
 			slog.Error("failed to rollback transaction", "err", err)
 		}
 	}()
@@ -433,7 +433,7 @@ func PromoteCustomService(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	defer func() {
-		if err := tx.Rollback(r.Context()); err != nil && err.Error() != "tx is closed" {
+		if err := tx.Rollback(r.Context()); err != nil && !errors.Is(err, pgx.ErrTxClosed) {
 			slog.Error("failed to rollback transaction", "err", err)
 		}
 	}()
@@ -543,7 +543,7 @@ func DeleteCustomService(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	defer func() {
-		if err := tx.Rollback(r.Context()); err != nil && err.Error() != "tx is closed" {
+		if err := tx.Rollback(r.Context()); err != nil && !errors.Is(err, pgx.ErrTxClosed) {
 			slog.Error("failed to rollback transaction", "err", err)
 		}
 	}()

backend/handlers/admin/discount_campaigns.go

@@ -282,7 +282,7 @@ func CreateDiscountCampaign(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	defer func() {
-		if err := tx.Rollback(r.Context()); err != nil && err.Error() != "tx is closed" {
+		if err := tx.Rollback(r.Context()); err != nil && !errors.Is(err, pgx.ErrTxClosed) {
 			slog.Error("failed to rollback transaction", "err", err)
 		}
 	}()
@@ -520,7 +520,7 @@ func UpdateDiscountCampaign(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	defer func() {
-		if err := tx.Rollback(r.Context()); err != nil && err.Error() != "tx is closed" {
+		if err := tx.Rollback(r.Context()); err != nil && !errors.Is(err, pgx.ErrTxClosed) {
 			slog.Error("failed to rollback transaction", "err", err)
 		}
 	}()
@@ -648,7 +648,7 @@ func DeleteDiscountCampaign(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	defer func() {
-		if err := tx.Rollback(r.Context()); err != nil && err.Error() != "tx is closed" {
+		if err := tx.Rollback(r.Context()); err != nil && !errors.Is(err, pgx.ErrTxClosed) {
 			slog.Error("failed to rollback transaction", "err", err)
 		}
 	}()

backend/handlers/admin/patch_tests.go

@@ -5,12 +5,14 @@ import (
 	"crussell/internal/validators"
 	"database/sql"
 	"encoding/json"
+	"errors"
 	"log"
 	"log/slog"
 	"net/http"
 	"strconv"
 
 	"github.com/go-chi/chi/v5"
+	"github.com/jackc/pgx/v5"
 )
 
 // PatchTest represents a patch test definition
@@ -106,7 +108,7 @@ func CreatePatchTest(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	defer func() {
-		if err := tx.Rollback(r.Context()); err != nil && err.Error() != "tx is closed" {
+		if err := tx.Rollback(r.Context()); err != nil && !errors.Is(err, pgx.ErrTxClosed) {
 			slog.Error("failed to rollback transaction", "err", err)
 		}
 	}()
@@ -189,7 +191,7 @@ func UpdatePatchTest(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	defer func() {
-		if err := tx.Rollback(r.Context()); err != nil && err.Error() != "tx is closed" {
+		if err := tx.Rollback(r.Context()); err != nil && !errors.Is(err, pgx.ErrTxClosed) {
 			slog.Error("failed to rollback transaction", "err", err)
 		}
 	}()
@@ -222,7 +224,7 @@ func DeletePatchTest(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	defer func() {
-		if err := tx.Rollback(r.Context()); err != nil && err.Error() != "tx is closed" {
+		if err := tx.Rollback(r.Context()); err != nil && !errors.Is(err, pgx.ErrTxClosed) {
 			slog.Error("failed to rollback transaction", "err", err)
 		}
 	}()

backend/handlers/admin/settings.go

@@ -3,6 +3,7 @@ package admin
 import (
 	"crussell/db"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"log"
 	"log/slog"
@@ -10,6 +11,8 @@ import (
 	"net/url"
 	"strconv"
 	"strings"
+
+	"github.com/jackc/pgx/v5"
 )
 
 type BusinessSettings struct {
@@ -250,7 +253,7 @@ func UpdateBusinessSettings(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	defer func() {
-		if err := tx.Rollback(r.Context()); err != nil && err.Error() != "tx is closed" {
+		if err := tx.Rollback(r.Context()); err != nil && !errors.Is(err, pgx.ErrTxClosed) {
 			slog.Error("failed to rollback transaction", "err", err)
 		}
 	}()