chore: support deploying with express mode api key

Author: yeesian

src/google/adk/cli/cli_deploy.py

@@ -838,7 +838,7 @@ def to_agent_engine(
     artifact_service_uri: Optional[str] = None,
     adk_version: Optional[str] = None,
 ):
-  """Deploys an agent to Vertex AI Agent Engine.
+  """Deploys an agent to Agent Platform Runtime.
 
   `agent_folder` should contain the following files:
 
@@ -1104,19 +1104,33 @@ def to_agent_engine(
 
     from ..utils._google_client_headers import get_tracking_headers
 
-    if not project or not region:
-      click.echo('No project/region provided. Starting onboarding flow...')
+    if not (api_key or project or region):
+      click.echo(
+          'No apikey/project/region provided. Starting onboarding flow...'
+      )
       auth_info = _onboarding.handle_login_with_google()
       project = auth_info.project_id
       region = auth_info.region
 
-    click.echo('Initializing Vertex AI...')
-    client = vertexai.Client(
-        project=project,
-        location=region,
-        http_options={'headers': get_tracking_headers()},
-    )
-    click.echo('Vertex AI initialized.')
+    click.echo('Initializing Agent Platform client...')
+    if project and region:
+      client = vertexai.Client(
+          project=project,
+          location=region,
+          http_options={'headers': get_tracking_headers()},
+      )
+    elif api_key:
+      client = vertexai.Client(
+          api_key=api_key,
+          http_options={'headers': get_tracking_headers()},
+      )
+    else:
+      click.echo(
+          'Failed to initialize Agent Platform client. Please provide an API'
+          'key or project and region.'
+      )
+      return
+    click.echo('Agent Platform client initialized.')
 
     if skip_agent_import_validation:
       warnings.warn(