WebDAV: Support auto indexing/importing in a sub-directory on a shared domain #2391

[chain710]

fix automatic indexing/importing not working in sub-directory

related discussion: #2386

Acceptance Criteria:

• Features and improvements are fully implemented so that they can be released at any time without additional work
• Automated unit and/or acceptance tests have been added to ensure the changes work as expected and to reduce repetitive manual work
• User interface changes are fully responsive and have been tested on all major browsers and various devices
• Database-related changes are compatible with SQLite and MariaDB
• Translations have been / will be updated (specify if needed)
• Documentation has been / will be updated (specify if needed)
• Contributor License Agreement (CLA) has been signed

[CLAassistant]

All committers have signed the CLA.

[lastzero]

Thank you! Next time, please do not commit your debug logs 👍 I'll merge this anyway to save time and then remove them locally...