Support custom agentless UFC endpoints

Author: leoromanovsky

products/feature-flagging/feature-flagging-lib/src/main/java/com/datadog/featureflag/AgentlessConfigurationSource.java

@@ -242,7 +242,11 @@ private void updateEtag(final String nextEtag) {
   }
 
   static HttpUrl endpoint(final Config config) {
-    final String endpoint = datadogApiServerDistributionEndpoint(config);
+    final String configuredBaseUrl = config.getFeatureFlaggingConfigurationSourceAgentlessBaseUrl();
+    final String endpoint =
+        configuredBaseUrl == null
+            ? datadogApiServerDistributionEndpoint(config)
+            : endpointFromConfiguredBaseUrl(configuredBaseUrl);
     final HttpUrl parsed = HttpUrl.parse(endpoint);
     if (parsed == null) {
       throw new IllegalArgumentException(
@@ -251,6 +255,22 @@ static HttpUrl endpoint(final Config config) {
     return parsed;
   }
 
+  private static String endpointFromConfiguredBaseUrl(final String configuredBaseUrl) {
+    final HttpUrl parsed = HttpUrl.parse(configuredBaseUrl.trim());
+    if (parsed == null) {
+      throw new IllegalArgumentException(
+          "Invalid Feature Flagging HTTP configuration source URL: " + configuredBaseUrl);
+    }
+    if ("/".equals(parsed.encodedPath()) || parsed.encodedPath().isEmpty()) {
+      return parsed
+          .newBuilder()
+          .addPathSegments(DATADOG_API_SERVER_DISTRIBUTION_PATH.substring(1))
+          .build()
+          .toString();
+    }
+    return parsed.toString();
+  }
+
   private static String datadogApiServerDistributionEndpoint(final Config config) {
     final StringBuilder endpoint =
         new StringBuilder("https://api.")

products/feature-flagging/feature-flagging-lib/src/test/java/com/datadog/featureflag/AgentlessConfigurationSourceTest.java

@@ -74,6 +74,41 @@ void derivesDatadogApiServerDistributionEndpointWithoutEnv() {
         AgentlessConfigurationSource.endpoint(config("datadoghq.com", null)).toString());
   }
 
+  @Test
+  void appendsServerDistributionPathToConfiguredAgentlessBaseUrl() {
+    final Config config = config();
+    lenient()
+        .when(config.getFeatureFlaggingConfigurationSourceAgentlessBaseUrl())
+        .thenReturn("http://mock-backend:8080");
+
+    assertEquals(
+        "http://mock-backend:8080/api/v2/feature-flagging/config/server-distribution",
+        AgentlessConfigurationSource.endpoint(config).toString());
+  }
+
+  @Test
+  void usesConfiguredAgentlessEndpointWithPathUnchanged() {
+    final Config config = config();
+    lenient()
+        .when(config.getFeatureFlaggingConfigurationSourceAgentlessBaseUrl())
+        .thenReturn("http://mock-backend:8080/custom/ufc?tenant=test");
+
+    assertEquals(
+        "http://mock-backend:8080/custom/ufc?tenant=test",
+        AgentlessConfigurationSource.endpoint(config).toString());
+  }
+
+  @Test
+  void rejectsInvalidConfiguredAgentlessBaseUrl() {
+    final Config config = config();
+    lenient()
+        .when(config.getFeatureFlaggingConfigurationSourceAgentlessBaseUrl())
+        .thenReturn("not a URL");
+
+    assertThrows(
+        IllegalArgumentException.class, () -> AgentlessConfigurationSource.endpoint(config));
+  }
+
   @Test
   void rejectsInvalidDatadogApiServerDistributionEndpoint() {
     assertThrows(
@@ -702,6 +737,7 @@ private static Config config(final String site, final String env) {
     lenient()
         .when(config.getFeatureFlaggingConfigurationSourceRequestTimeoutSeconds())
         .thenReturn(2);
+    lenient().when(config.getFeatureFlaggingConfigurationSourceAgentlessBaseUrl()).thenReturn(null);
     lenient().when(config.getApiKey()).thenReturn("test-api-key");
     lenient().when(config.getSite()).thenReturn(site);
     lenient().when(config.getEnv()).thenReturn(env);