Add support for custom CloseableHttpClient for Proxy Support (#441)

## Summary
- Adding additional newDefaultInstance method to support custom CloseableHttpClient object
- Allows for customs object to support Proxy Settings

Customer support

## Test plan
- FSC and TestCase added
## Issues
- "OASIS-7899"

Author: The-inside-man

core-httpclient-impl/src/main/java/com/optimizely/ab/OptimizelyFactory.java

@@ -23,6 +23,7 @@
 import com.optimizely.ab.event.EventHandler;
 import com.optimizely.ab.internal.PropertyUtils;
 import com.optimizely.ab.notification.NotificationCenter;
+import org.apache.http.impl.client.CloseableHttpClient;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -247,11 +248,26 @@ public static Optimizely newDefaultInstance(String sdkKey, String fallback) {
      * @return A new Optimizely instance
      */
     public static Optimizely newDefaultInstance(String sdkKey, String fallback, String datafileAccessToken) {
+        return newDefaultInstance(sdkKey, fallback, datafileAccessToken, null);
+    }
+    
+    /**
+     * Returns a new Optimizely instance with authenticated datafile support.
+     *
+     * @param sdkKey   SDK key used to build the ProjectConfigManager.
+     * @param fallback Fallback datafile string used by the ProjectConfigManager to be immediately available.
+     * @param datafileAccessToken  Token for authenticated datafile access.
+     * @param customHttpClient  Customizable CloseableHttpClient to build OptimizelyHttpClient.
+     * @return A new Optimizely instance
+     */
+    public static Optimizely newDefaultInstance(String sdkKey, String fallback, String datafileAccessToken, CloseableHttpClient customHttpClient) {
         NotificationCenter notificationCenter = new NotificationCenter();
-
-        HttpProjectConfigManager.Builder builder = HttpProjectConfigManager.builder()
+        OptimizelyHttpClient optimizelyHttpClient = new OptimizelyHttpClient(customHttpClient);
+        HttpProjectConfigManager.Builder builder;
+        builder = HttpProjectConfigManager.builder()
             .withDatafile(fallback)
             .withNotificationCenter(notificationCenter)
+            .withOptimizelyHttpClient(customHttpClient == null ? null : optimizelyHttpClient)
             .withSdkKey(sdkKey);
 
         if (datafileAccessToken != null) {

core-httpclient-impl/src/test/java/com/optimizely/ab/OptimizelyFactoryTest.java

@@ -23,6 +23,12 @@
 import com.optimizely.ab.event.BatchEventProcessor;
 import com.optimizely.ab.internal.PropertyUtils;
 import com.optimizely.ab.notification.NotificationCenter;
+import org.apache.http.HttpHost;
+import org.apache.http.conn.routing.HttpRoutePlanner;
+import org.apache.http.impl.client.CloseableHttpClient;
+import org.apache.http.impl.client.HttpClientBuilder;
+import org.apache.http.impl.client.HttpClients;
+import org.apache.http.impl.conn.DefaultProxyRoutePlanner;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
@@ -237,6 +243,24 @@ public void newDefaultInstanceWithDatafileAccessToken() throws Exception {
         assertTrue(optimizely.isValid());
     }
 
+    @Test
+    public void newDefaultInstanceWithDatafileAccessTokenAndCustomHttpClient() throws Exception {
+        // Add custom Proxy and Port here
+        int port = 443;
+        String proxyHostName = "someProxy.com";
+        HttpHost proxyHost = new HttpHost(proxyHostName, port);
+
+        HttpRoutePlanner routePlanner = new DefaultProxyRoutePlanner(proxyHost);
+
+        HttpClientBuilder clientBuilder = HttpClients.custom();
+        clientBuilder = clientBuilder.setRoutePlanner(routePlanner);
+
+        CloseableHttpClient httpClient = clientBuilder.build();
+        String datafileString = Resources.toString(Resources.getResource("valid-project-config-v4.json"), Charsets.UTF_8);
+        optimizely = OptimizelyFactory.newDefaultInstance("sdk-key", datafileString, "auth-token", httpClient);
+        assertTrue(optimizely.isValid());
+    }
+
     @Test
     public void newDefaultInstanceWithProjectConfig() throws Exception {
         optimizely = OptimizelyFactory.newDefaultInstance(() -> null);