Attach from WebDAV and save to WebDAV not available in mobile apps

Description:

When a user has added a WebDAV storage (Nextcloud integration), he is still not able to attach files from his WebDAV storage or save attachments to his WebDAV storage.

The context menu for "add attachment" is missing the WebDAV entry. The context menu for an existing attachment is missing the "Save to WebDAV" menu entry.

Environment Information:

• Rocket.Chat Server Version: 3.7.0
• Rocket.Chat App Version: 4.11.0
• Device Name: iPhone, iPad
• OS Version: 14.0.1

Steps to reproduce:

1. Long click on an attachment (voice message, picture, video ...)
2. Check context menu
3. "Save to WebDAV" is missing although the user has an active WebDAV storage (it works in the browser)

1. Click on "+" in the compose window
2. Check context menu
3. "Choose from WebDAV" is missing although the user has an active WebDAV storage (it works in the browser)

Expected behavior:

WebDAV integration should exspecially be available in the mobile apps where up/download from and to the device is very limited!

Actual behavior:

Both optiona are missing (see above)

Start by locating the mobile attachment context menus for adding files and for existing attachments, then compare their available actions with the browser's WebDAV behavior described in the issue. Done means users with an active WebDAV storage can choose files from it and save existing attachments to it in the iPhone and iPad apps.