Add ByteString IsUTF8 (#1470)

* Add ByteString IsUTF8

* Add Test for Return Type of IsUtf8()

src/core/etl/src/Flow/ETL/Function/IsUtf8.php

@@ -0,0 +1,34 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Flow\ETL\Function;
+
+use function Flow\ETL\DSL\{type_boolean};
+use function Symfony\Component\String\{b};
+use Flow\ETL\Function\ScalarFunction\TypedScalarFunction;
+use Flow\ETL\PHP\Type\Type;
+use Flow\ETL\Row;
+
+final class IsUtf8 extends ScalarFunctionChain implements TypedScalarFunction
+{
+    public function __construct(private readonly ScalarFunction|string $string)
+    {
+    }
+
+    public function eval(Row $row) : mixed
+    {
+        $string = (new Parameter($this->string))->asString($row);
+
+        if ($string === null) {
+            return null;
+        }
+
+        return b($string)->isUtf8();
+    }
+
+    public function returns() : Type
+    {
+        return type_boolean();
+    }
+}

src/core/etl/src/Flow/ETL/Function/ScalarFunctionChain.php

@@ -316,6 +316,11 @@ public function isType(string|Type ...$types) : self
         return new IsType($this, ...$types);
     }
 
+    public function isUtf8() : IsUtf8
+    {
+        return new IsUtf8($this);
+    }
+
     public function jsonDecode(ScalarFunction|int $flags = JSON_THROW_ON_ERROR) : self
     {
         return new JsonDecode($this, $flags);

src/core/etl/tests/Flow/ETL/Tests/Unit/Function/IsUtf8Test.php

@@ -0,0 +1,39 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Flow\ETL\Tests\Unit\Function;
+
+use function Flow\ETL\DSL\row;
+use function Flow\ETL\DSL\{ref, str_entry, type_boolean};
+use Flow\ETL\Function\IsUtf8;
+use Flow\ETL\PHP\Type\Type;
+use Flow\ETL\Tests\FlowTestCase;
+
+final class IsUtf8Test extends FlowTestCase
+{
+    public function test_is_utf_8() : void
+    {
+        self::assertTrue(
+            ref('str')->isUtf8()->eval(
+                row(str_entry('str', 'Lorem Ipsum'))
+            )
+        );
+
+        self::assertFalse(
+            ref('str')->isUtf8()->eval(
+                row(str_entry('str', "\xc3\x28"))
+            )
+        );
+    }
+
+    public function test_returns_method_returns_string_boolean() : void
+    {
+        $isUtf8Function = new IsUtf8('Lorem Ipsum');
+        $returnType = $isUtf8Function->returns();
+
+        self::assertInstanceOf(Type::class, $returnType);
+
+        self::assertTrue($returnType->isEqual(type_boolean()));
+    }
+}