Feat: add initial Google Drive connector support (#11147)

### What problem does this PR solve?

This feature is primarily ported from the
[Onyx](https://github.com/onyx-dot-app/onyx) project with necessary
modifications. Thanks for such a brilliant project.

Minor: consistently use `google_drive` rather than `google_driver`.

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src="https://github.com/user-attachments/assets/6f64e70e-881e-42c7-b45f-809d3e0024a4"
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src="https://github.com/user-attachments/assets/dfa7d1ef-819a-4a82-8c52-0999f48ed4a6"
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src="https://github.com/user-attachments/assets/39e792fb-9fbe-4f3d-9b3c-b2265186bc22"
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src="https://github.com/user-attachments/assets/27d70e96-d9c0-42d9-8c89-276919b6d61d"
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### Type of change

- [x] New Feature (non-breaking change which adds functionality)

common/data_source/config.py

@@ -42,6 +42,8 @@ class DocumentSource(str, Enum):
     OCI_STORAGE = "oci_storage"
     SLACK = "slack"
     CONFLUENCE = "confluence"
+    GOOGLE_DRIVE = "google_drive"
+    GMAIL = "gmail"
     DISCORD = "discord"
 
 
@@ -100,22 +102,6 @@ NOTION_CONNECTOR_DISABLE_RECURSIVE_PAGE_LOOKUP = (
     == "true"
 )
 
-# This is the Oauth token
-DB_CREDENTIALS_DICT_TOKEN_KEY = "google_tokens"
-# This is the service account key
-DB_CREDENTIALS_DICT_SERVICE_ACCOUNT_KEY = "google_service_account_key"
-# The email saved for both auth types
-DB_CREDENTIALS_PRIMARY_ADMIN_KEY = "google_primary_admin"
-
-USER_FIELDS = "nextPageToken, users(primaryEmail)"
-
-# Error message substrings
-MISSING_SCOPES_ERROR_STR = "client not authorized for any of the scopes requested"
-
-SCOPE_INSTRUCTIONS = (
-    "You have upgraded RAGFlow without updating the Google Auth scopes. "
-)
-
 SLIM_BATCH_SIZE = 100
 
 # Notion API constants
@@ -184,6 +170,10 @@ CONFLUENCE_TIMEZONE_OFFSET = float(
     os.environ.get("CONFLUENCE_TIMEZONE_OFFSET", get_current_tz_offset())
 )
 
+GOOGLE_DRIVE_CONNECTOR_SIZE_THRESHOLD = int(
+    os.environ.get("GOOGLE_DRIVE_CONNECTOR_SIZE_THRESHOLD", 10 * 1024 * 1024)
+)
+
 OAUTH_SLACK_CLIENT_ID = os.environ.get("OAUTH_SLACK_CLIENT_ID", "")
 OAUTH_SLACK_CLIENT_SECRET = os.environ.get("OAUTH_SLACK_CLIENT_SECRET", "")
 OAUTH_CONFLUENCE_CLOUD_CLIENT_ID = os.environ.get(