fix: update index to be serialized in __sleep() (#12366)

Signed-off-by: Vikram Vaswani <2571660+vvaswani@users.noreply.github.com`>

Author: vvaswani

src/Mapping/FieldMapping.php

@@ -142,7 +142,7 @@ public function __sleep(): array
     {
         $serialized = ['type', 'fieldName', 'columnName'];
 
-        foreach (['nullable', 'notInsertable', 'notUpdatable', 'id', 'unique', 'version', 'quoted'] as $boolKey) {
+        foreach (['nullable', 'notInsertable', 'notUpdatable', 'id', 'unique', 'version', 'quoted', 'index'] as $boolKey) {
             if ($this->$boolKey) {
                 $serialized[] = $boolKey;
             }

tests/Tests/ORM/Mapping/FieldMappingTest.php

@@ -33,6 +33,7 @@ public function testItSurvivesSerialization(): void
         $mapping->precision        = 10;
         $mapping->scale            = 2;
         $mapping->unique           = true;
+        $mapping->index            = true;
         $mapping->inherited        = self::class;
         $mapping->originalClass    = self::class;
         $mapping->originalField    = 'id';
@@ -57,6 +58,7 @@ public function testItSurvivesSerialization(): void
         self::assertSame(10, $resurrectedMapping->precision);
         self::assertSame(2, $resurrectedMapping->scale);
         self::assertTrue($resurrectedMapping->unique);
+        self::assertTrue($resurrectedMapping->index);
         self::assertSame(self::class, $resurrectedMapping->inherited);
         self::assertSame(self::class, $resurrectedMapping->originalClass);
         self::assertSame('id', $resurrectedMapping->originalField);