added possibility to pass custom base url

Author: yevheniyJ

src/main/java/com/crowdin/client/core/CrowdinApi.java

@@ -34,10 +34,18 @@ public CrowdinApi(Credentials credentials, ClientConfig clientConfig) {
             this.httpClient = clientConfig.getHttpClient();
         }
         this.clientConfig = clientConfig;
-        if (credentials.getOrganization() != null) {
-            this.url = "https://" + credentials.getOrganization() + ".api.crowdin.com/api/v2";
+        if (clientConfig.getBaseUrl() != null) {
+            if (clientConfig.getBaseUrl().endsWith("/")) {
+                this.url = clientConfig.getBaseUrl() + "api/v2";
+            } else {
+                this.url = clientConfig.getBaseUrl() + "/api/v2";
+            }
         } else {
-            this.url = "https://api.crowdin.com/api/v2";
+            if (credentials.getOrganization() != null) {
+                this.url = "https://" + credentials.getOrganization() + ".api.crowdin.com/api/v2";
+            } else {
+                this.url = "https://api.crowdin.com/api/v2";
+            }
         }
     }
 }

src/main/java/com/crowdin/client/core/model/ClientConfig.java

@@ -28,4 +28,8 @@ public class ClientConfig {
      * Provide custom json transformer
      */
     private JsonTransformer jsonTransformer;
+    /**
+     * Base url of the server
+     */
+    private String baseUrl;
 }