feat(strings/uuidv7): add UUIDv7 generation (#10)

The UUID v7 format is a time-ordered random UUID. It uses a timestamp
with millisecond precision in the most significant bits, followed by
random data. This provides both uniqueness and chronological ordering,
making it ideal for database primary keys and situations where sorting
by creation time is desired.

References:
- https://uuid7.com/
- https://www.ietf.org/archive/id/draft-peabody-dispatch-new-uuid-format-04.html#name-uuid-version-7

strings.go

@@ -7,6 +7,8 @@ import (
 	"fmt"
 	"math/big"
 	"unicode"
+
+	"github.com/jimeh/rands/uuid"
 )
 
 const (
@@ -18,7 +20,6 @@ const (
 	alphabeticChars   = upperChars + lowerChars
 	alphanumericChars = alphabeticChars + numericChars
 	dnsLabelChars     = lowerNumericChars + "-"
-	uuidHyphen        = byte('-')
 )
 
 var (
@@ -237,27 +238,33 @@ func DNSLabel(n int) (string, error) {
 // UUID returns a random UUID v4 in string format as defined by RFC 4122,
 // section 4.4.
 func UUID() (string, error) {
-	b, err := Bytes(16)
+	uuid, err := uuid.NewRandom()
 	if err != nil {
 		return "", err
 	}
 
-	b[6] = (b[6] & 0x0f) | 0x40 // Version: 4 (random)
-	b[8] = (b[8] & 0x3f) | 0x80 // Variant: RFC 4122
+	return uuid.String(), nil
+}
 
-	// Construct a UUID v4 string according to RFC 4122 specifications.
-	dst := make([]byte, 36)
-	hex.Encode(dst[0:8], b[0:4]) // time-low
-	dst[8] = uuidHyphen
-	hex.Encode(dst[9:13], b[4:6]) // time-mid
-	dst[13] = uuidHyphen
-	hex.Encode(dst[14:18], b[6:8]) // time-high-and-version
-	dst[18] = uuidHyphen
-	hex.Encode(dst[19:23], b[8:10]) // clock-seq-and-reserved, clock-seq-low
-	dst[23] = uuidHyphen
-	hex.Encode(dst[24:], b[10:]) // node
+// UUIDv7 returns a time-ordered UUID v7 in string format.
+//
+// The UUID v7 format uses a timestamp with millisecond precision in the most
+// significant bits, followed by random data. This provides both uniqueness and
+// chronological ordering, making it ideal for database primary keys and
+// situations where sorting by creation time is desired.
+//
+// References:
+// - https://uuid7.com/
+// - https://www.ietf.org/archive/id/draft-peabody-dispatch-new-uuid-format-04.html#name-uuid-version-7
+//
+//nolint:lll
+func UUIDv7() (string, error) {
+	uuid, err := uuid.NewV7()
+	if err != nil {
+		return "", err
+	}
 
-	return string(dst), nil
+	return uuid.String(), nil
 }
 
 func isASCII(s string) bool {