add renew authentication endpoint

Author: lbalmaceda

README.md

@@ -226,6 +226,24 @@ try {
 }
 ```
 
+### Renew Authentication
+
+Creates a new request to renew the authentication and get fresh new credentials using a valid Refresh Token.
+
+`AuthRequest renewAuth(String refreshToken)`
+
+Example:
+```java
+AuthRequest request = auth.renewAuth("nisd1h9dks1doWJOsaf");
+try {
+    TokenHolder holder = request.execute();
+} catch (APIException exception) {
+    // api error
+} catch (Auth0Exception exception) {
+    // request error
+}
+```
+
 
 ## Management API
 

src/main/java/com/auth0/client/auth/AuthAPI.java

@@ -25,6 +25,7 @@ public class AuthAPI {
     private static final String KEY_EMAIL = "email";
     private static final String KEY_CONNECTION = "connection";
     private static final String KEY_TOKEN = "token";
+    private static final String KEY_REFRESH_TOKEN = "refresh_token";
 
     private static final String PATH_OAUTH = "oauth";
     private static final String PATH_TOKEN = "token";
@@ -442,6 +443,41 @@ public Request<Void> revokeToken(String refreshToken) {
         return request;
     }
 
+
+    /**
+     * Creates a new request to renew the authentication and get fresh new credentials using a valid Refresh Token and the 'refresh_token' grant.
+     * <pre>
+     * {@code
+     * AuthAPI auth = new AuthAPI("me.auth0.com", "B3c6RYhk1v9SbIJcRIOwu62gIUGsnze", "2679NfkaBn62e6w5E8zNEzjr-yWfkaBne");
+     * try {
+     *      TokenHolder result = auth.renewAuth("ej2E8zNEzjrcSD2edjaE")
+     *          .execute();
+     * } catch (Auth0Exception e) {
+     *      //Something happened
+     * }
+     * }
+     * </pre>
+     *
+     * @param refreshToken the refresh token to use to get fresh new credentials.
+     * @return a Request to configure and execute.
+     */
+    public AuthRequest renewAuth(String refreshToken) {
+        Asserts.assertNotNull(refreshToken, "refresh token");
+
+        String url = HttpUrl.parse(baseUrl)
+                .newBuilder()
+                .addPathSegment(PATH_OAUTH)
+                .addPathSegment(PATH_TOKEN)
+                .build()
+                .toString();
+        TokenRequest request = new TokenRequest(client, url);
+        request.addParameter(KEY_CLIENT_ID, clientId);
+        request.addParameter(KEY_CLIENT_SECRET, clientSecret);
+        request.addParameter(KEY_GRANT_TYPE, "refresh_token");
+        request.addParameter(KEY_REFRESH_TOKEN, refreshToken);
+        return request;
+    }
+
     /**
      * Creates a new request to exchange the code obtained in the /authorize call using the 'Authorization Code' grant.
      * <pre>

src/test/java/com/auth0/client/auth/AuthAPITest.java

@@ -714,7 +714,6 @@ public void shouldCreateLogInWithClientCredentialsGrantRequest() throws Exceptio
 
     //Revoke a Token
 
-
     @Test
     public void shouldThrowOnRevokeTokenWithNullToken() throws Exception {
         exception.expect(IllegalArgumentException.class);
@@ -742,4 +741,40 @@ public void shouldCreateRevokeTokenRequest() throws Exception {
         assertThat(response, is(nullValue()));
     }
 
+
+    //Renew Authentication using Refresh Token
+
+    @Test
+    public void shouldThrowOnRenewAuthWithNullRefreshToken() throws Exception {
+        exception.expect(IllegalArgumentException.class);
+        exception.expectMessage("'refresh token' cannot be null!");
+        api.renewAuth(null);
+    }
+
+    @Test
+    public void shouldCreateRenewAuthRequest() throws Exception {
+        AuthRequest request = api.renewAuth("ej2E8zNEzjrcSD2edjaE");
+        assertThat(request, is(notNullValue()));
+
+        server.jsonResponse(AUTH_TOKENS, 200);
+        TokenHolder response = request.execute();
+        RecordedRequest recordedRequest = server.takeRequest();
+
+        assertThat(recordedRequest, hasMethodAndPath("POST", "/oauth/token"));
+        assertThat(recordedRequest, hasHeader("Content-Type", "application/json"));
+
+        Map<String, Object> body = bodyFromRequest(recordedRequest);
+        assertThat(body, hasEntry("grant_type", (Object) "refresh_token"));
+        assertThat(body, hasEntry("client_id", (Object) CLIENT_ID));
+        assertThat(body, hasEntry("client_secret", (Object) CLIENT_SECRET));
+        assertThat(body, hasEntry("refresh_token", (Object) "ej2E8zNEzjrcSD2edjaE"));
+
+        assertThat(response, is(notNullValue()));
+        assertThat(response.getAccessToken(), not(isEmptyOrNullString()));
+        assertThat(response.getIdToken(), not(isEmptyOrNullString()));
+        assertThat(response.getRefreshToken(), not(isEmptyOrNullString()));
+        assertThat(response.getTokenType(), not(isEmptyOrNullString()));
+        assertThat(response.getExpiresIn(), is(notNullValue()));
+    }
+
 }