Fix the payload used to add a label to an issue

src/main/java/io/spring/issuebot/github/GitHubTemplate.java

@@ -127,10 +127,8 @@ public class GitHubTemplate implements GitHubOperations {
 
 	@Override
 	public Issue addLabel(Issue issue, String labelName) {
-		Map<String, Object> body = new HashMap<>();
-		body.put("labels", Arrays.asList(labelName));
 		ResponseEntity<Label[]> response = this.rest.exchange(
-				new RequestEntity<>(body, HttpMethod.POST,
+				new RequestEntity<>(Arrays.asList(labelName), HttpMethod.POST,
 						URI.create(issue.getLabelsUrl().replace("{/name}", ""))),
 				Label[].class);
 		if (response.getStatusCode() != HttpStatus.OK) {

src/test/java/io/spring/issuebot/github/GitHubTemplateTests.java

@@ -159,8 +159,8 @@ public class GitHubTemplateTests {
 	@Test
 	public void addLabelToIssue() {
 		this.server.expect(requestTo("labelsUrl")).andExpect(method(HttpMethod.POST))
-				.andExpect(basicAuth())
-				.andExpect(content().string("{\"labels\":[\"test\"]}")).andRespond(
+				.andExpect(basicAuth()).andExpect(content().string("[\"test\"]"))
+				.andRespond(
 						withSuccess("[{\"name\":\"test\"}]", MediaType.APPLICATION_JSON));
 		Issue issue = new Issue("issueUrl", null, null, "labelsUrl{/name}", null, null,
 				null, null);