fix: Use PostgreSQL hex format for bytea literals (fixes #32) (#71)

Replace invalid b"..." format with PostgreSQL-compatible '\x...' hex format
for bytea literals. The old format caused syntax errors when executing
queries with byte values.

Changes:
- Add encoding/hex import to cel2sql.go
- Update bytea literal generation to use '\x' + hex encoding
- Remove unused bytesToOctets function from utils.go
- Update test expectations to match new hex format

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <noreply@anthropic.com>

Author: richardwooding

cel2sql.go

@@ -3,6 +3,7 @@ package cel2sql
 
 import (
 	"context"
+	"encoding/hex"
 	"errors"
 	"fmt"
 	"log/slog"
@@ -1534,9 +1535,9 @@ func (con *converter) visitConst(expr *exprpb.Expr) error {
 			con.str.WriteString(fmt.Sprintf("$%d", con.paramCount))
 			con.parameters = append(con.parameters, b)
 		} else {
-			con.str.WriteString(`b"`)
-			con.str.WriteString(bytesToOctets(b))
-			con.str.WriteString(`"`)
+			con.str.WriteString("'\\x")
+			con.str.WriteString(hex.EncodeToString(b))
+			con.str.WriteString("'")
 		}
 	default:
 		return newConversionErrorf(errMsgUnsupportedExpression, "constant type: %T", c.ConstantKind)

edgecase_coverage_test.go

@@ -115,7 +115,7 @@ func TestConstEdgeCases(t *testing.T) {
 		{
 			name:        "bytes_value",
 			expression:  `b"hello" != b""`,
-			expectedSQL: `b"\150\145\154\154\157" != b""`,
+			expectedSQL: `'\x68656c6c6f' != '\x'`,
 			description: "Bytes constant",
 		},
 		{

final_coverage_test.go

@@ -287,7 +287,7 @@ func TestBinaryOperatorAdditionalCases(t *testing.T) {
 		{
 			name:        "bytes_concatenation",
 			expression:  `b"hello" + b" world" != b""`,
-			expectedSQL: `b"\150\145\154\154\157" || b"\040\167\157\162\154\144" != b""`,
+			expectedSQL: `'\x68656c6c6f' || '\x20776f726c64' != '\x'`,
 			description: "Bytes concatenation with || operator",
 		},
 		{

utils.go

@@ -148,18 +148,6 @@ func extractFieldName(node *exprpb.Expr) (string, error) {
 	return fieldName, nil
 }
 
-// Byte conversion utilities
-
-// bytesToOctets converts byte sequences to a string using a three digit octal encoded value
-// per byte.
-func bytesToOctets(byteVal []byte) string {
-	var b strings.Builder
-	for _, c := range byteVal {
-		_, _ = fmt.Fprintf(&b, "\\%03o", c)
-	}
-	return b.String()
-}
-
 // Numeric comparison utilities
 
 // isNumericComparison checks if an operator is a numeric comparison