[Feature Request]: Support custom CA certificate / SSL verification option for WebDAV connector

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Is your feature request related to a problem?

`webdav_connector.py` instantiates the WebDAV client without any SSL verification override:


self.client = WebDAVClient(base_url=self.base_url, auth=(username, password))


This means `httpx`'s default certificate verification against public root CAs is always used. Self-hosted WebDAV servers (OpenMediaVault, Synology NAS, home-lab Nextcloud/Apache instances, etc.) very commonly use self-signed certificates, since they're not exposed to the public internet. In that case, the connection fails with an SSL certificate verification error, and the WebDAV data source cannot sync at all.

The only current workaround is to patch the source file directly to pass a `verify=` argument pointing to a local CA bundle. This requires shell access to the container and isn't upgrade-safe — reapplying the patch after an image update without checking for an existing `verify=` argument can result in a duplicate keyword argument and a hard SyntaxError that crashes the entire RAGFlow backend on startup.

Describe the feature you'd like

Add an optional field to the WebDAV data source configuration (both in the connector class and the corresponding UI form), e.g.:

• ca_cert_path (string, optional): path to a custom CA certificate/bundle mounted into the container, passed as verify=ca_cert_path to WebDAVClient.
• Alternatively/additionally, a verify_ssl boolean toggle (default true) to allow disabling verification entirely for quick testing, with a clear warning in the UI about the security implications.

This would let self-hosted users configure trust for their own certificate directly through the data source settings, without touching source code.

Describe implementation you've considered

Manually patching webdav_connector.py and bind-mounting the patched file in docker-compose.yml to survive image updates. Functional, but fragile and not discoverable for most users, and error-prone if the patch is reapplied without checking whether a verify= argument already exists.

Documentation, adoption, use case

Example: a home-lab user running RAGFlow in Docker, connecting to a WebDAV share on OpenMediaVault (or Synology, self-hosted Nextcloud, etc.) secured with a self-signed certificate. Currently the only path forward is to patch source code inside the container. Related connectors in the same codebase (S3/blob, Seafile) may have similar needs for self-hosted/on-premise deployments with internal CAs.

Additional information

Happy to provide the exact traceback and reproduction steps from a real-world OMV setup if useful.

Start with webdav_connector.py and the corresponding WebDAV data source UI form, then trace how connector settings reach WebDAVClient. Compare the optional CA path and SSL toggle requested in the issue, including the UI warning for disabled verification. Done means users can configure a self-hosted WebDAV certificate without patching source files.