fix: complete stable32 backport coverage for ServerSignatureDate

Signed-off-by: Vitor Mattos <1079143+vitormattos@users.noreply.github.com>

Author: vitormattos

lib/Service/SignatureTextService.php

@@ -185,7 +185,7 @@ public function getAvailableVariables(): array {
 			'{{LocalSignerSignatureDateOnly}}' => $this->l10n->t('Date when the signer sent the request to sign (without time, in their local time zone).'),
 			'{{LocalSignerSignatureDateTime}}' => $this->l10n->t('Date and time when the signer sent the request to sign (in their local time zone).'),
 			'{{LocalSignerTimezone}}' => $this->l10n->t('Time zone of signer when sent the request to sign (in their local time zone).'),
-			'{{ServerSignatureDate}}' => $this->l10n->t('Date and time when the signature was applied on the server. Cannot be formatted using Twig.'),
+			'{{ServerSignatureDate}}' => $this->l10n->t('Date and time when the signature was applied on the server (ISO 8601 format). Can be formatted using the Twig date filter.'),
 			'{{SignerCommonName}}' => $this->l10n->t('Common Name (CN) used to identify the document signer.'),
 			'{{SignerEmail}}' => $this->l10n->t('The signer\'s email is optional and can be left blank.'),
 			'{{SignerIdentifier}}' => $this->l10n->t('Unique information used to identify the signer (such as email, phone number, or username).'),

tests/php/Unit/Handler/SignEngine/JSignPdfHandlerTest.php

@@ -733,14 +733,45 @@ public function testGetSignatureTextWithTwigDateFilterAndTimezone(): void {
 		$this->assertMatchesRegularExpression('/^"\d{2}\/\d{2}\/\d{4} \d{2}:\d{2}:\d{2} [A-Z]{3,4}"$/', $actual);
 	}
 
+	public function testGetSignatureTextWithTwigDateFilterWithoutTimezone(): void {
+		$this->appConfig->setValueString(
+			'libresign',
+			'signature_text_template',
+			'{{ ServerSignatureDate|date("d/m/Y") }}'
+		);
+		$this->appConfig->setValueString('libresign', 'signature_render_mode', SignerElementsService::RENDER_MODE_DESCRIPTION_ONLY);
+
+		$jSignPdfHandler = $this->getInstance();
+		$actual = $jSignPdfHandler->getSignatureText();
+
+		$this->assertMatchesRegularExpression('/^"\d{2}\/\d{2}\/\d{4}"$/', $actual);
+	}
+
+	public function testGetSignatureTextGraphicOnlyWithTwigDateFilterAlwaysReturnsEmpty(): void {
+		$this->appConfig->setValueString(
+			'libresign',
+			'signature_text_template',
+			'{{ ServerSignatureDate|date("d/m/Y H:i:s T", "Europe/Paris") }}'
+		);
+		$this->appConfig->setValueString('libresign', 'signature_render_mode', SignerElementsService::RENDER_MODE_GRAPHIC_ONLY);
+
+		$jSignPdfHandler = $this->getInstance();
+		$actual = $jSignPdfHandler->getSignatureText();
+
+		$this->assertSame('""', $actual);
+	}
+
 	public static function providerGetSignatureText(): array {
 		return [
 			['FAKE_RENDER_MODE', '',     '""'],
 			['FAKE_RENDER_MODE', 'a',    '"a"'],
 			['FAKE_RENDER_MODE', "a\na", "\"a\na\""],
 			['FAKE_RENDER_MODE', 'a"a',  '"a\"a"'],
 			['FAKE_RENDER_MODE', 'a$a',  '"a\$a"'],
+			// Plain {{ServerSignatureDate}} (no spaces) preserves JSign placeholder
 			['FAKE_RENDER_MODE', '{{ServerSignatureDate}}', '"\${timestamp}"'],
+			// Plain {{ ServerSignatureDate }} (with spaces) also preserves JSign placeholder
+			['FAKE_RENDER_MODE', '{{ ServerSignatureDate }}', '"\${timestamp}"'],
 			['GRAPHIC_ONLY',     '',     '""'],
 			['GRAPHIC_ONLY',     'a',    '""'],
 			['GRAPHIC_ONLY',     "a\na", '""'],