Add support to get a user installation for the authenticated app

src/main/java/com/spotify/github/v3/clients/GitHubClient.java

@@ -431,8 +431,13 @@
     return OrganisationClient.create(this, org);
   }
 
-  public UserClient createUserClient() {
-    return UserClient.create(this);
+  /**
+  * Create user API client
+  *
+  * @return user API client
+  */
+  public UserClient createUserClient(final String owner) {
+    return UserClient.create(this, owner);
   }
 
   Json json() {

src/main/java/com/spotify/github/v3/clients/GithubAppClient.java

@@ -45,6 +45,7 @@ public class GithubAppClient {
     refer to the organisation in the installation endpoint
   */
   private static final String GET_INSTALLATION_ORG_URL = "/orgs/%s/installation";
+  private static final String GET_INSTALLATION_USER_URL = "/users/%s/installation";
 
   private final GitHubClient github;
   private final String owner;
@@ -114,6 +115,15 @@ private CompletableFuture<Installation> getOrgInstallation() {
         String.format(GET_INSTALLATION_ORG_URL, owner), Installation.class);
   }
 
+    /**
+   * Get an installation of a user
+   * @return an Installation
+   */
+  public CompletableFuture<Installation> getUserInstallation() {
+    return github.request(
+        String.format(GET_INSTALLATION_USER_URL, owner), Installation.class);
+  }
+
   /**
    * Authenticates as an installation
    *

src/main/java/com/spotify/github/v3/clients/UserClient.java

@@ -27,15 +27,21 @@
 
   public static final int NO_CONTENT = 204;
   private final GitHubClient github;
+  private final String owner;
 
   private static final String SUSPEND_USER_TEMPLATE = "/users/%s/suspended";
 
-  UserClient(final GitHubClient github) {
+  UserClient(final GitHubClient github, final String owner) {
     this.github = github;
+    this.owner = owner;
   }
 
-  static UserClient create(final GitHubClient github) {
-    return new UserClient(github);
+  static UserClient create(final GitHubClient github, final String owner) {
+    return new UserClient(github, owner);
+  }
+
+  public GithubAppClient createGithubAppClient() {
+    return new GithubAppClient(this.github, this.owner);
   }
 
   /**

src/test/java/com/spotify/github/v3/clients/UserClientTest.java

@@ -19,16 +19,25 @@
  */
 package com.spotify.github.v3.clients;
 
+import static com.google.common.io.Resources.getResource;
+import static java.nio.charset.Charset.defaultCharset;
 import static java.util.concurrent.CompletableFuture.completedFuture;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.core.Is.is;
 import static org.junit.jupiter.api.Assertions.*;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 
+import com.google.common.io.Resources;
 import com.spotify.github.jackson.Json;
+import com.spotify.github.v3.checks.Installation;
 import com.spotify.github.v3.user.requests.ImmutableSuspensionReason;
+
+import java.io.IOException;
 import java.util.concurrent.CompletableFuture;
+
 import okhttp3.Response;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
@@ -37,12 +46,17 @@ public class UserClientTest {
 
     private GitHubClient github;
     private UserClient userClient;
+    private String owner = "github";
+    private Json json;
+    private static String getFixture(String resource) throws IOException {
+        return Resources.toString(getResource(TeamClientTest.class, resource), defaultCharset());
+    }
 
     @BeforeEach
     public void setUp() {
         github = mock(GitHubClient.class);
-        userClient = new UserClient(github);
-        Json json = Json.create();
+        userClient = new UserClient(github, owner);
+        json = Json.create();
         when(github.json()).thenReturn(json);
     }
 
@@ -81,4 +95,17 @@ public void testUnSuspendUserFailure() throws Exception {
         final CompletableFuture<Boolean> result = userClient.unSuspendUser("username", ImmutableSuspensionReason.builder().reason("That's why").build());
         assertFalse(result.get());
     }
+
+    @Test
+    public void testAppClient() throws Exception {
+        final GithubAppClient githubAppClient = userClient.createGithubAppClient();
+        final CompletableFuture<Installation> fixture =
+                completedFuture(json.fromJson(getFixture("../githubapp/installation.json"), Installation.class));
+        when(github.request("/users/github/installation", Installation.class)).thenReturn(fixture);
+
+        final Installation installation = githubAppClient.getUserInstallation().get();
+
+        assertThat(installation.id(), is(1));
+        assertThat(installation.account().login(), is("github"));
+    }
 }