Allow to add public shared folders to be used on desktop client

[mgallien]

General feature description in nextcloud/files-clients#9

Someone shares you a folder via public link and you want to interact with it.
Currently you are limited to use web only.

Idea is now to allow all clients to add this public link and use it like a real account

click add public link
enter url
now you can change between your real Nextcloud accounts and those public shares
    browsing on mobile
    uploading
    even auto upload files into it

On server (and thus then a separate issue):

on all public shared folders offer "add to clients"
    via e.g. special nc://share/ protocol clients can directly add it

This is first a rough idea, some things are to consider

how to check/show if a share is not available
proper handle read-only shares
do not allow re-shares

[mgallien]

@nimishavijay @jancborchardt
I will try to come up with some very basic ideas on how to integrate this and will need your feedback
if you have already suggestions or ideas you are very welcome !

[tobiasKaminsky]

In systray

• show "folder with link" icon in account overview
  • first line: public link name
  • second line: shared by user xy, replaces status
  • third line: instance address
• in activity show only file/folder activity
• hide: set status, log out
• change: "remove account" to "leave share"
• remove apps (like Talk, app dropdown) if account is selected

Context menu of file browser:

• hide: share options
• hide: copy internal link

[lauff]

It seems that there is a pull request available, but it unfortunately is not incorporated for quite a while. Is there anything I (we) can help with?