Include optional attribute in model for path and req param descriptors

spring-restdocs-core/src/main/java/org/springframework/restdocs/request/AbstractParametersSnippet.java

@@ -189,6 +189,7 @@ public abstract class AbstractParametersSnippet extends TemplatedSnippet {
 		Map<String, Object> model = new HashMap<>();
 		model.put("name", descriptor.getName());
 		model.put("description", descriptor.getDescription());
+		model.put("optional", descriptor.isOptional());
 		model.putAll(descriptor.getAttributes());
 		return model;
 	}

spring-restdocs-core/src/test/java/org/springframework/restdocs/request/RequestParametersSnippetTests.java

@@ -163,6 +163,25 @@ public class RequestParametersSnippetTests extends AbstractSnippetTests {
 												.build());
 	}
 
+	@Test
+	public void requestParametersWithOptionalColumn() throws IOException {
+		TemplateResourceResolver resolver = mock(TemplateResourceResolver.class);
+		given(resolver.resolveTemplateResource("request-parameters"))
+				.willReturn(snippetResource("request-parameters-with-optional-column"));
+		this.snippet.expectRequestParameters("request-parameters-with-optional-column")
+				.withContents(tableWithHeader("Parameter", "Optional", "Description")
+						.row("a", "true", "one").row("b", "false", "two"));
+
+		new RequestParametersSnippet(Arrays.asList(
+				parameterWithName("a").description("one").optional(),
+				parameterWithName("b").description("two"))).document(
+						operationBuilder("request-parameters-with-optional-column")
+								.attribute(TemplateEngine.class.getName(),
+										new MustacheTemplateEngine(resolver))
+								.request("http://localhost").param("a", "alpha")
+								.param("b", "bravo").build());
+	}
+
 	@Test
 	public void additionalDescriptors() throws IOException {
 		this.snippet.expectRequestParameters("additional-descriptors")

spring-restdocs-core/src/test/resources/custom-snippet-templates/asciidoctor/request-parameters-with-optional-column.snippet

@@ -0,0 +1,10 @@
+|===
+|Parameter|Optional|Description
+
+{{#parameters}}
+|{{name}}
+|{{optional}}
+|{{description}}
+
+{{/parameters}}
+|===

spring-restdocs-core/src/test/resources/custom-snippet-templates/markdown/request-parameters-with-optional-column.snippet

@@ -0,0 +1,5 @@
+Parameter | Optional | Description
+--------- | -------- | -----------
+{{#parameters}}
+{{name}} | {{optional}} | {{description}}
+{{/parameters}}