Feature/add refresh access token method to api client (#88)

* Split up method so that we can re-use the logic to retrieve a new access token using a refresh token instead of authorization code

* Removed note about not being allowed to edit the ApiClient class

* Putting the code in the right array index

* Cleaned up imports

* Removed blank line

src/Client/ApiClient.php

@@ -20,21 +20,13 @@
  * Generated by: https://github.com/swagger-api/swagger-codegen.git
  */
 
-/**
- * NOTE: This class is auto generated by the swagger code generator program.
- * https://github.com/swagger-api/swagger-codegen
- * Do not edit the class manually.
- */
-
 namespace DocuSign\eSign\Client;
 
 use DocuSign\eSign\Client\Auth\OAuth;
-use \DocuSign\eSign\Configuration;
-use \DocuSign\eSign\ObjectSerializer;
-use SebastianBergmann\RecursionContext\InvalidArgumentException;
+use DocuSign\eSign\Configuration;
+use DocuSign\eSign\ObjectSerializer;
 use Firebase\JWT\JWT;
 
-
 /**
  * ApiClient Class Doc Comment
  *
@@ -378,7 +370,7 @@ public function selectHeaderContentType($content_type)
      *
      * @param string $raw_headers A string of raw HTTP response headers
      *
-     * @return string[] Array of HTTP response heaers
+     * @return string[] Array of HTTP response headers
      */
     protected function httpParseHeaders($raw_headers)
     {
@@ -449,26 +441,29 @@ public function getAuthorizationURI($client_id, $scopes, $redirect_uri, $respons
     }
 
     /**
-     * GenerateAccessToken will exchange the authorization code for an access token and refresh tokens.
-     *
+     * @param string $grant_type Should be either "authorization_code" or "refresh_token".
      * @param string $client_id DocuSign OAuth Client Id(AKA Integrator Key)
      * @param string $client_secret The secret key you generated when you set up the integration in DocuSign Admin console.
-     * @param string $code The authorization code
+     * @param string $code Depending on the grant_type this should be either the authorization code or the refresh token.
      *
      * @return array
      * @throws ApiException
-     * @throws InvalidArgumentException
+     * @throws \InvalidArgumentException
      */
-    public function generateAccessToken($client_id = null, $client_secret = null, $code = null)
+    private function accessToken($grant_type, $client_id = null, $client_secret = null, $code = null)
     {
+        $caller = debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS,2)[1]['function'];
+        if ($grant_type !== "authorization_code" && $grant_type !== "refresh_token") {
+            throw new \InvalidArgumentException('Grant type should be either "authorization_code" or "refresh_token"');
+        }
         if (!$client_id) {
-            throw new \InvalidArgumentException('Missing the required parameter $client_id when calling generateAccessToken');
+            throw new \InvalidArgumentException("Missing the required parameter $client_id when calling {$caller}");
         }
         if (!$client_secret || !$code) {
-            throw new \InvalidArgumentException('Missing the required parameter $client_secret when calling generateAccessToken');
+            throw new \InvalidArgumentException("Missing the required parameter $client_secret when calling {$caller}");
         }
         if (!$code) {
-            throw new \InvalidArgumentException('Missing the required parameter $code when calling generateAccessToken');
+            throw new \InvalidArgumentException("Missing the required parameter $code when calling {$caller}");
         }
 
         $resourcePath = "/oauth/token";
@@ -479,15 +474,53 @@ public function generateAccessToken($client_id = null, $client_secret = null, $c
             "Content-Type" => "application/x-www-form-urlencoded",
         ];
         $postData = [
-            "grant_type" => "authorization_code",
-            "code" => $code
+            "grant_type" => $grant_type
         ];
+
+        if ($grant_type === 'authorization_code') {
+            $postData['code'] = $code;
+        } elseif ($grant_type === 'refresh_token') {
+            $postData['refresh_token'] = $code;
+        }
+
         list($response, $statusCode, $httpHeader) = $this->callApi($resourcePath, self::$POST, $queryParams, $postData, $headers, null, null, true);
         if(isset($response->access_token))
             $this->config->addDefaultHeader("Authorization", "{$response->token_type} {$response->access_token}");
         return [$this->getSerializer()->deserialize($response, '\DocuSign\eSign\Client\Auth\OAuthToken', $httpHeader), $statusCode, $httpHeader];
     }
 
+    /**
+     * generateAccessToken will exchange the authorization code for an access token and a refresh token.
+     *
+     * @param string $client_id DocuSign OAuth Client Id(AKA Integrator Key)
+     * @param string $client_secret The secret key you generated when you set up the integration in DocuSign Admin console.
+     * @param string $authorization_code The authorization code.
+     *
+     * @return array
+     * @throws ApiException
+     * @throws \InvalidArgumentException
+     */
+    public function generateAccessToken($client_id = null, $client_secret = null, $authorization_code = null)
+    {
+        return $this->accessToken("authorization_code", $client_id, $client_secret, $authorization_code);
+    }
+
+    /**
+     * refreshAccessToken will exchange the refresh token for a new access token and a new refresh token.
+     *
+     * @param string $client_id DocuSign OAuth Client Id(AKA Integrator Key)
+     * @param string $client_secret The secret key you generated when you set up the integration in DocuSign Admin console.
+     * @param string $refresh_token The refresh token.
+     *
+     * @return array
+     * @throws ApiException
+     * @throws \InvalidArgumentException
+     */
+    public function refreshAccessToken($client_id = null, $client_secret = null, $refresh_token = null)
+    {
+        return $this->accessToken("refresh_token", $client_id, $client_secret, $refresh_token);
+    }
+
     /**
      * Request JWT User Token
      *
@@ -498,7 +531,7 @@ public function generateAccessToken($client_id = null, $client_secret = null, $c
      * @param  int $expires_in Number of minutes token will be valid
      * @return array
      * @throws ApiException
-     * @throws InvalidArgumentException
+     * @throws \InvalidArgumentException
      */
     public function requestJWTUserToken($client_id, $user_id, $rsa_private_key, $scopes = null, $expires_in = 60)
     {