[CHA-1558] support ext custom header (#230)

* [CHA-1558] support ext custom header

* fix format

---------

Co-authored-by: Rafael Marinho <rafael.marinho@getstream.io>

Author: rafaelmf3

src/main/java/io/getstream/chat/java/services/framework/DefaultClient.java

@@ -32,6 +32,7 @@ public class DefaultClient implements Client {
   public static final String API_SECRET_PROP_NAME = "io.getstream.chat.apiSecret";
   public static final String API_TIMEOUT_PROP_NAME = "io.getstream.chat.timeout";
   public static final String API_URL_PROP_NAME = "io.getstream.chat.url";
+  public static final String X_STREAM_EXT_PROP_NAME = "io.getstream.chat.xStreamExt";
 
   private static final String API_DEFAULT_URL = "https://chat.stream-io-api.com";
   private static volatile DefaultClient defaultInstance;
@@ -121,6 +122,12 @@ private OkHttpClient buildOkHttpClient() {
                   .header("X-Stream-Client", "stream-java-client-" + sdkVersion)
                   .header("Stream-Auth-Type", "jwt");
 
+          // Add x-stream-ext header if configured
+          String xStreamExt = getXStreamExt(extendedProperties);
+          if (xStreamExt != null && !xStreamExt.isEmpty()) {
+            builder.header("X-Stream-Ext", xStreamExt);
+          }
+
           if (userToken != null) {
             // User token present - use user auth
             builder.header("Authorization", userToken.value());
@@ -231,6 +238,13 @@ private static Properties extendProperties(Properties properties) {
       canformedProperties.put(API_URL_PROP_NAME, envApiUrl);
     }
 
+    var envXStreamExt =
+        env.getOrDefault(
+            "STREAM_CHAT_X_STREAM_EXT", System.getProperty("STREAM_CHAT_X_STREAM_EXT"));
+    if (envXStreamExt != null) {
+      canformedProperties.put(X_STREAM_EXT_PROP_NAME, envXStreamExt);
+    }
+
     canformedProperties.putAll(System.getProperties());
     canformedProperties.putAll(properties);
     return canformedProperties;
@@ -246,6 +260,11 @@ private static String getStreamChatBaseUrl(@NotNull Properties properties) {
     return url.toString();
   }
 
+  private static String getXStreamExt(@NotNull Properties properties) {
+    var xStreamExt = properties.get(X_STREAM_EXT_PROP_NAME);
+    return xStreamExt != null ? xStreamExt.toString() : null;
+  }
+
   private static final @NotNull String sdkVersion = getSdkVersion();
 
   private static @NotNull String getSdkVersion() {