fix: ClientContext(sdkKey) test ctor generates a single instance id (SDK-2356)

Previously the public single-arg `ClientContext(String sdkKey)` test-convenience
constructor produced an internally inconsistent state: `defaultHttp(sdkKey)`
built an HttpConfiguration whose default headers embedded one auto-generated
UUID (via the inner minimalContext), and the outer delegated 8-arg constructor
auto-generated a separate UUID for `this.instanceId`. As a result,
`context.getInstanceId()` and `context.getHttp().getDefaultHeaders()` returned
different values for `X-LaunchDarkly-Instance-Id` -- so consumer code that
read the instance id via the getter would see a different identifier than the
SDK actually placed on outbound requests.

Generate the UUID once in a new private delegating constructor and thread it
both into `defaultHttp(sdkKey, instanceId)` (so the headers carry it) and
into the explicit instanceId argument of the 9-arg constructor (so the
accessor returns the same value).

Added a regression test in ClientContextImplTest that asserts these two
accessors agree.

Author: keelerm84

lib/sdk/server/src/main/java/com/launchdarkly/sdk/server/subsystems/ClientContext.java

@@ -129,20 +129,32 @@ protected ClientContext(ClientContext copyFrom) {
    * @param sdkKey the SDK key
    */
   public ClientContext(String sdkKey) {
+    this(sdkKey, UUID.randomUUID().toString());
+  }
+
+  // Private delegating constructor: generates a single instance id up front and threads it
+  // both into the default HttpConfiguration (so the X-LaunchDarkly-Instance-Id default
+  // header carries it) and into this.instanceId (so getInstanceId() returns the same value).
+  // The earlier shape, where the public single-arg ctor called defaultHttp(sdkKey) and then
+  // let the eight-arg ctor auto-generate a fresh UUID, produced two different ids -- one in
+  // the headers and one returned by getInstanceId().
+  private ClientContext(String sdkKey, String instanceId) {
     this(
         sdkKey,
         new ApplicationInfo(null, null),
-        defaultHttp(sdkKey),
+        defaultHttp(sdkKey, instanceId),
         defaultLogging(),
         false,
         Components.serviceEndpoints().createServiceEndpoints(),
         Thread.MIN_PRIORITY,
-      null
+        null,
+        instanceId
         );
   }
-  
-  private static HttpConfiguration defaultHttp(String sdkKey) {
-    ClientContext minimalContext = new ClientContext(sdkKey, null, null, null, false, null, 0, null);
+
+  private static HttpConfiguration defaultHttp(String sdkKey, String instanceId) {
+    ClientContext minimalContext = new ClientContext(sdkKey, null, null, null, false, null, 0, null,
+        instanceId);
     return Components.httpConfiguration().build(minimalContext);
   }
 

lib/sdk/server/src/test/java/com/launchdarkly/sdk/server/ClientContextImplTest.java

@@ -96,15 +96,46 @@ public void packagePrivatePropertiesHaveDefaultsIfContextIsNotOurImplementation(
     // This covers a scenario where a user has created their own ClientContext and it has been
     // passed to one of our SDK components.
     ClientContext c = new ClientContext(SDK_KEY);
-    
+
     ClientContextImpl impl = ClientContextImpl.get(c);
-    
+
     assertNotNull(impl.sharedExecutor);
     assertNull(impl.diagnosticStore);
-    
+
     ClientContextImpl impl2 = ClientContextImpl.get(c);
-    
+
     assertNotNull(impl2.sharedExecutor);
     assertSame(impl.sharedExecutor, impl2.sharedExecutor);
   }
+
+  // Exercises the test-convenience constructor `new ClientContext(String)` that consumers of
+  // the SDK use when wiring up custom data sources, stores, etc. Bugbot flagged that this
+  // constructor produces an internally-inconsistent instance id: the headers carried by the
+  // HttpConfiguration (built inside defaultHttp(sdkKey)) embed one UUID, while
+  // getInstanceId() returns a different UUID generated by the delegated 8-arg constructor.
+  @Test
+  public void instanceIdIsConsistentBetweenAccessorAndDefaultHeaders() {
+    ClientContext c = new ClientContext(SDK_KEY);
+
+    String accessorValue = c.getInstanceId();
+    assertNotNull("ClientContext should expose a non-null instance id", accessorValue);
+
+    String headerValue = null;
+    for (java.util.Map.Entry<String, String> entry : c.getHttp().getDefaultHeaders()) {
+      if ("X-LaunchDarkly-Instance-Id".equalsIgnoreCase(entry.getKey())) {
+        headerValue = entry.getValue();
+        break;
+      }
+    }
+    assertNotNull(
+        "HttpConfiguration default headers should include X-LaunchDarkly-Instance-Id",
+        headerValue);
+
+    assertEquals(
+        "getInstanceId() should match the value attached to X-LaunchDarkly-Instance-Id on "
+            + "the default headers — otherwise outbound requests will not carry the same id "
+            + "that consumer code reads via getInstanceId().",
+        accessorValue,
+        headerValue);
+  }
 }