Add unit tests for X-Databricks-Workspace-Id header gating in AppsImpl

* `testWorkspaceIdHeaderSentWhenConfigured` — when ApiClient#workspaceId()
  returns a value, a workspace-scoped impl forwards it on the
  X-Databricks-Workspace-Id request header.
* `testWorkspaceIdHeaderOmittedWhenUnset` — when ApiClient#workspaceId()
  returns null, the header is not sent (so calls to legacy single-workspace
  hosts don't pick up an empty value).

AppsImpl is one representative of the generator-emitted workspace-scoped
shape; if the generator template regresses on either branch (drops the
header, misspells it, or skips the null guard) the next regen would reshape
AppsImpl and at least one assertion would fail.

Signed-off-by: Divyansh Vijayvergia <divyansh.vijayvergia@databricks.com>

Author: Divyansh-db

databricks-sdk-java/src/test/java/com/databricks/sdk/service/apps/AppsImplTest.java

@@ -41,4 +41,42 @@ public void testCreateAppIncludesNoComputeParameter() throws IOException {
                 }),
             eq(App.class));
   }
+
+  // On unified ("SPOG") hosts, workspace-scoped requests must carry an
+  // X-Databricks-Workspace-Id header so the gateway can route them to the
+  // correct workspace. When ApiClient#workspaceId() returns a value, every
+  // generated *Impl must forward it on the request; when it returns null,
+  // the header must be omitted (so calls to legacy single-workspace hosts
+  // don't pick up an empty value).
+  @Test
+  public void testWorkspaceIdHeaderSentWhenConfigured() throws IOException {
+    ApiClient apiClient = Mockito.mock(ApiClient.class);
+    when(apiClient.workspaceId()).thenReturn("7474644166319138");
+    when(apiClient.execute(any(), any())).thenReturn(null);
+
+    AppsService apps = new AppsImpl(apiClient);
+    apps.list(new ListAppsRequest());
+
+    verify(apiClient)
+        .execute(
+            argThat(
+                (Request req) ->
+                    "7474644166319138".equals(req.getHeaders().get("X-Databricks-Workspace-Id"))),
+            any());
+  }
+
+  @Test
+  public void testWorkspaceIdHeaderOmittedWhenUnset() throws IOException {
+    ApiClient apiClient = Mockito.mock(ApiClient.class);
+    when(apiClient.workspaceId()).thenReturn(null);
+    when(apiClient.execute(any(), any())).thenReturn(null);
+
+    AppsService apps = new AppsImpl(apiClient);
+    apps.list(new ListAppsRequest());
+
+    verify(apiClient)
+        .execute(
+            argThat((Request req) -> !req.getHeaders().containsKey("X-Databricks-Workspace-Id")),
+            any());
+  }
 }