N°6414 Move existing AbstractSimpleField::Validate impl to custom validators

- LinkedSetField
- SelectObjectField
- MultipleChoicesField (warning this hierarchy contains non multiple value fields like SelectField !)

Also change AbstractValidator::Validate signature : now we are returning an array of error messages, so that we can return multiple ones

tests/php-unit-tests/unitary-tests/sources/Form/SelectObjectFieldTest.php

@@ -0,0 +1,43 @@
+<?php
+/*
+ * @copyright   Copyright (C) 2010-2023 Combodo SARL
+ * @license     http://opensource.org/licenses/AGPL-3.0
+ */
+
+namespace Form;
+
+use Combodo\iTop\Form\Field\SelectObjectField;
+use Combodo\iTop\Test\UnitTest\ItopDataTestCase;
+use ContextTag;
+use DBObjectSearch;
+use Organization;
+
+class SelectObjectFieldTest extends ItopDataTestCase {
+	public function testValidate(): void {
+		$oSelectObjectField = new SelectObjectField('test');
+		$oSelectObjectField->SetSearch(DBObjectSearch::FromOQL('SELECT '.Organization::class));
+
+		// N°1150 the control was added for the REST API initially and was only triggered with the corresponding ContextTag
+		$oRestContext = new ContextTag(ContextTag::TAG_REST);
+		$this->ValidateSelectObjectField($oSelectObjectField);
+
+		// retrying without REST context
+		unset($oRestContext);
+		$this->ValidateSelectObjectField($oSelectObjectField);
+	}
+
+	private function ValidateSelectObjectField(SelectObjectField $oSelectObjectField): void {
+		$oSelectObjectField->SetCurrentValue(null);
+		$this->assertTrue($oSelectObjectField->Validate(), 'No value must be valid');
+
+		$sExistingOrganizationId = 1;
+		$oSelectObjectField->SetCurrentValue($sExistingOrganizationId);
+		$this->assertTrue($oSelectObjectField->Validate(), 'An existing object id must be valid');
+
+		$sNonExistingOrganizationId = 999999;
+		$oSelectObjectField->SetCurrentValue($sNonExistingOrganizationId);
+		$this->assertFalse($oSelectObjectField->Validate(), 'An non existing object id must be invalid');
+		$this->assertCount(1, $oSelectObjectField->GetErrorMessages());
+		$this->assertStringContainsString($sNonExistingOrganizationId, $oSelectObjectField->GetErrorMessages()[0]);
+	}
+}