Add response_type and custom parameter setter for AuthorizeUrlBuilder

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

@@ -38,8 +38,8 @@ private AuthorizeUrlBuilder(String domain, String clientId, String redirectUri)
         builder = HttpUrl.parse(domain).newBuilder()
                 .addPathSegment("authorize")
                 .addEncodedQueryParameter("redirect_uri", redirectUri)
-                .addQueryParameter("response_type", "code")
                 .addQueryParameter("client_id", clientId);
+        withParameter("response_type", "code");
     }
 
     /**
@@ -90,6 +90,32 @@ public AuthorizeUrlBuilder withScope(String scope) {
         return this;
     }
 
+    /**
+     * Sets the response type value.
+     *
+     * @param responseType response type to set
+     * @return the builder instance
+     */
+    public AuthorizeUrlBuilder withResponseType(String responseType) {
+        assertNotNull(responseType, "response type");
+        parameters.put("response_type", responseType);
+        return this;
+    }
+
+    /**
+     * Sets an additional parameter.
+     *
+     * @param name  name of the parameter
+     * @param value value of the parameter to set
+     * @return the builder instance
+     */
+    public AuthorizeUrlBuilder withParameter(String name, String value) {
+        assertNotNull(name, "name");
+        assertNotNull(value, "value");
+        parameters.put(name, value);
+        return this;
+    }
+
     /**
      * Creates a string representation of the URL with the configured parameters.
      *

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

@@ -156,11 +156,50 @@ public void shouldSetScope() throws Exception {
     }
 
     @Test
-    public void shouldThrowWithStateIsNull() throws Exception {
+    public void shouldThrowWhenScopeIsNull() throws Exception {
         exception.expect(IllegalArgumentException.class);
-        exception.expectMessage("'state' cannot be null!");
+        exception.expectMessage("'scope' cannot be null!");
         AuthorizeUrlBuilder.newInstance(DOMAIN, CLIENT_ID, REDIRECT_URI)
-                .withState(null);
+                .withScope(null);
+    }
+
+    @Test
+    public void shouldSetResponseType() throws Exception {
+        String url = AuthorizeUrlBuilder.newInstance(DOMAIN, CLIENT_ID, REDIRECT_URI)
+                .withResponseType("token id_token")
+                .build();
+        assertThat(url, hasQueryParameter("response_type", "token id_token"));
+    }
+
+    @Test
+    public void shouldThrowWhenResponseTypeIsNull() throws Exception {
+        exception.expect(IllegalArgumentException.class);
+        exception.expectMessage("'response type' cannot be null!");
+        AuthorizeUrlBuilder.newInstance(DOMAIN, CLIENT_ID, REDIRECT_URI)
+                .withResponseType(null);
+    }
+
+    @Test
+    public void shouldSetCustomParameter() throws Exception {
+        String url = AuthorizeUrlBuilder.newInstance(DOMAIN, CLIENT_ID, REDIRECT_URI)
+                .withParameter("name", "value")
+                .build();
+        assertThat(url, hasQueryParameter("name", "value"));
     }
 
+    @Test
+    public void shouldThrowWhenCustomParameterNameIsNull() throws Exception {
+        exception.expect(IllegalArgumentException.class);
+        exception.expectMessage("'name' cannot be null!");
+        AuthorizeUrlBuilder.newInstance(DOMAIN, CLIENT_ID, REDIRECT_URI)
+                .withParameter(null, "value");
+    }
+
+    @Test
+    public void shouldThrowWhenCustomParameterValueIsNull() throws Exception {
+        exception.expect(IllegalArgumentException.class);
+        exception.expectMessage("'value' cannot be null!");
+        AuthorizeUrlBuilder.newInstance(DOMAIN, CLIENT_ID, REDIRECT_URI)
+                .withParameter("name", null);
+    }
 }