feat!: default to Firebase backend. (#86)

The Cloud Debugger API is shut down, so all agents must use the Firebase
backend.

requirements.txt

@@ -1,6 +1,2 @@
-google-auth>=1.0.0
-google-auth-httplib2
-google-api-python-client
-google-api-core
 firebase_admin>=5.3.0
 pyyaml

src/googleclouddebugger/__init__.py

@@ -29,7 +29,6 @@
 from . import breakpoints_manager
 from . import collector
 from . import error_data_visibility_policy
-from . import gcp_hub_client
 from . import firebase_client
 from . import glob_data_visibility_policy
 from . import yaml_data_visibility_config_reader
@@ -52,20 +51,10 @@ def _StartDebugger():
   cdbg_native.LogInfo(
       f'Initializing Cloud Debugger Python agent version: {__version__}')
 
-  use_firebase = _flags.get('use_firebase')
-  if use_firebase:
-    _backend_client = firebase_client.FirebaseClient()
-    _backend_client.SetupAuth(
-        _flags.get('project_id'), _flags.get('service_account_json_file'),
-        _flags.get('firebase_db_url'))
-  else:
-    _backend_client = gcp_hub_client.GcpHubClient()
-    _backend_client.SetupAuth(
-        _flags.get('project_id'), _flags.get('project_number'),
-        _flags.get('service_account_json_file'))
-    _backend_client.SetupCanaryMode(
-        _flags.get('breakpoint_enable_canary'),
-        _flags.get('breakpoint_allow_canary_override'))
+  _backend_client = firebase_client.FirebaseClient()
+  _backend_client.SetupAuth(
+      _flags.get('project_id'), _flags.get('service_account_json_file'),
+      _flags.get('firebase_db_url'))
 
   visibility_policy = _GetVisibilityPolicy()