feat(integrations): add Dropbox connection test and global-credential sharing

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

app/api/dropbox.py

@@ -23,6 +23,81 @@ logger = logging.getLogger(__name__)
 router = APIRouter()
 
 
+@router.get("/dropbox/global-authorize-url")
+@require_login
+async def dropbox_global_authorize_url(request: Request):
+    """Return the Dropbox OAuth authorization URL using the global app credentials.
+
+    This endpoint is used when ``DROPBOX_ALLOW_GLOBAL_CREDENTIALS_FOR_INTEGRATIONS``
+    is enabled so that users can authorize their personal Dropbox integration without
+    needing to supply their own app key/secret.  Only the public ``app_key`` is
+    embedded in the URL; the ``app_secret`` is never sent to the browser.
+    """
+    if not settings.dropbox_allow_global_credentials_for_integrations:
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="Global credentials for integrations are not enabled",
+        )
+    if not settings.dropbox_app_key or not settings.dropbox_app_secret:
+        raise HTTPException(
+            status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
+            detail="Global Dropbox credentials are not configured",
+        )
+    redirect_uri = str(request.base_url).rstrip("/") + "/dropbox-callback"
+    authorize_url = (
+        "https://www.dropbox.com/oauth2/authorize"
+        f"?client_id={settings.dropbox_app_key}"
+        "&response_type=code"
+        "&token_access_type=offline"
+        f"&redirect_uri={redirect_uri}"
+    )
+    return {"authorize_url": authorize_url}
+
+
+@router.post("/dropbox/exchange-token-global")
+@require_login
+async def exchange_dropbox_token_global(
+    request: Request,
+    code: Annotated[str, Form(...)],
+    redirect_uri: Annotated[str, Form(...)],
+):
+    """Exchange an authorization code using the global Dropbox app credentials.
+
+    Used when ``DROPBOX_ALLOW_GLOBAL_CREDENTIALS_FOR_INTEGRATIONS`` is enabled so
+    that the ``app_secret`` is never exposed to the browser.  Only the OAuth code
+    and redirect URI need to be supplied by the client.
+    """
+    if not settings.dropbox_allow_global_credentials_for_integrations:
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="Global credentials for integrations are not enabled",
+        )
+    if not settings.dropbox_app_key or not settings.dropbox_app_secret:
+        raise HTTPException(
+            status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
+            detail="Global Dropbox credentials are not configured",
+        )
+
+    token_url = "https://api.dropboxapi.com/oauth2/token"
+    payload = {
+        "client_id": settings.dropbox_app_key,
+        "client_secret": settings.dropbox_app_secret,
+        "code": code,
+        "redirect_uri": redirect_uri,
+        "grant_type": "authorization_code",
+    }
+
+    token_data = exchange_oauth_token(provider_name="Dropbox", token_url=token_url, payload=payload)
+
+    return {
+        "refresh_token": token_data["refresh_token"],
+        "access_token": token_data["access_token"],
+        "expires_in": token_data.get("expires_in", 14400),
+        # Return the public app_key so the callback can store it in the integration
+        "app_key": settings.dropbox_app_key,
+    }
+
+
 @router.post("/dropbox/exchange-token")
 @require_login
 async def exchange_dropbox_token(