Add Google Drive authorization processing and error handling templates

- Implemented `google_drive_callback.html` for processing Google Drive authorization, including UI for success and error states.
- Added JavaScript functionality for exchanging authorization codes, saving settings, and handling folder selection.
- Created `google_drive_callback_error.html` to display error messages during the authorization process.

app/views/google_drive.py

@@ -0,0 +1,118 @@
+"""
+Google Drive integration views for setup and OAuth callback.
+"""
+from fastapi import Request
+from fastapi.responses import RedirectResponse
+import urllib.parse
+
+from app.views.base import APIRouter, templates, require_login, settings
+
+router = APIRouter()
+
+@router.get("/google-drive-setup")
+@require_login
+async def google_drive_setup_page(request: Request):
+    """
+    Setup page for the Google Drive integration.
+    Shows configuration status and setup instructions.
+    """
+    # Check if using OAuth
+    use_oauth = getattr(settings, 'google_drive_use_oauth', False)
+    
+    # Check Google Drive OAuth configuration
+    oauth_configured = bool(settings.google_drive_client_id and 
+                         settings.google_drive_client_secret and 
+                         settings.google_drive_refresh_token)
+    
+    # Check Google Drive service account configuration
+    sa_configured = bool(settings.google_drive_credentials_json)
+    
+    # Overall configuration status
+    is_configured = (use_oauth and oauth_configured) or (not use_oauth and sa_configured)
+    
+    if settings.google_drive_folder_id:
+        is_configured = is_configured and True
+    else:
+        is_configured = False
+    
+    # Get configuration values to display status (hide sensitive values)
+    return templates.TemplateResponse(
+        "google_drive.html",
+        {
+            "request": request,
+            "is_configured": is_configured,
+            "use_oauth": use_oauth,
+            "oauth_configured": oauth_configured,
+            "sa_configured": sa_configured,
+            "client_id": bool(settings.google_drive_client_id),
+            "client_id_value": settings.google_drive_client_id or "",
+            "client_secret": bool(settings.google_drive_client_secret),
+            "client_secret_value": settings.google_drive_client_secret or "",
+            "refresh_token": bool(settings.google_drive_refresh_token),
+            "refresh_token_value": settings.google_drive_refresh_token or "",
+            "folder_id": settings.google_drive_folder_id or "",
+            "has_credentials_json": bool(settings.google_drive_credentials_json)
+        }
+    )
+
+@router.get("/google-drive-callback")
+@require_login
+async def google_drive_callback(request: Request, code: str = None, error: str = None, state: str = None):
+    """
+    Callback endpoint for Google Drive OAuth flow.
+    Now automatically exchanges the code for a token and saves it to the configuration.
+    """
+    if error:
+        return templates.TemplateResponse(
+            "google_drive_callback_error.html",
+            {"request": request, "error": error}
+        )
+    
+    if not code:
+        return templates.TemplateResponse(
+            "google_drive_callback_error.html",
+            {"request": request, "error": "No authorization code received from Google"}
+        )
+    
+    # Display the processing page with automatic token exchange
+    return templates.TemplateResponse(
+        "google_drive_callback.html",
+        {
+            "request": request, 
+            "code": code,
+            "state": state
+        }
+    )
+
+@router.get("/google-drive-auth-start")
+@require_login
+async def google_drive_auth_start(
+    request: Request, 
+    client_id: str,
+    redirect_uri: str = None
+):
+    """
+    Start the Google Drive OAuth flow by redirecting to Google's authorization page.
+    """
+    if not redirect_uri:
+        redirect_uri = f"{request.url.scheme}://{request.url.netloc}/google-drive-callback"
+    
+    # Create the authorization URL with required scopes
+    # Use only drive.file scope to minimize required permissions
+    scopes = [
+        "https://www.googleapis.com/auth/drive.file"  # Access to files created or opened by the app
+    ]
+    
+    scope_str = urllib.parse.quote(' '.join(scopes))
+    
+    auth_url = (
+        f"https://accounts.google.com/o/oauth2/auth"
+        f"?client_id={client_id}"
+        f"&redirect_uri={urllib.parse.quote(redirect_uri)}"
+        f"&response_type=code"
+        f"&scope={scope_str}"
+        f"&access_type=offline"
+        f"&prompt=consent"  # Force to show consent screen to get refresh token
+    )
+    
+    return RedirectResponse(url=auth_url)