feat: registrationBegin method without email;

fix: missing sqlc query parameter name;
feat: util for generating security codes;
feat: enums package

backend/internal/utils/enums/enums.go

@@ -0,0 +1,8 @@
+package enums
+
+type ConfirmationCodeType int32
+
+const (
+	RegistrationCodeType ConfirmationCodeType = iota
+	PasswordResetCodeType
+)

backend/internal/utils/securityCode.go

@@ -0,0 +1,26 @@
+package utils
+
+import (
+	"crypto/rand"
+	"fmt"
+	"io"
+)
+
+func GenerateSecure6DigitNumber() (string, error) {
+	// Generate a random number between 0 and 999999 (inclusive)
+	// This ensures we get a 6-digit number, including those starting with 0
+	max := 1000000 // Upper bound (exclusive)
+	b := make([]byte, 4) // A 4-byte slice is sufficient for a 32-bit integer
+
+	if _, err := io.ReadFull(rand.Reader, b); err != nil {
+		return "", fmt.Errorf("failed to read random bytes: %w", err)
+	}
+
+	// Convert bytes to an integer
+	// We use a simple modulo operation to get a number within our desired range.
+	// While this introduces a slight bias for very large ranges, for 1,000,000
+	// it's negligible and simpler than more complex methods like rejection sampling.
+	num := int(uint32(b[0])<<24 | uint32(b[1])<<16 | uint32(b[2])<<8 | uint32(b[3])) % max
+
+	return fmt.Sprintf("%06d", num), nil
+}