Implement dynamic roles for server 10.3+ and oCIS

[HanaGemela]

Background is here https://github.com/owncloud/enterprise/issues/3473

Steps to recreate:

1. Connected to server 10.3+ and oCIS
2. Right click on a resource
3. Select Share from ownCloud submenu
4. Select Public links

Expected result: Roles are displayed instead of permissions

[pmaier1]

Expected result: Roles are displayed instead of permissions

One clarification: It is expected that the client makes use of the new (10.3) roles API (if the capability is present) in order to fetch the available permissions/roles (for public links and user/group sharing) from the server and to display them dynamically.

The main reasons that the roles API was implemented are

• We added a new role for public links. Clients can't implement it statically because its availability depends on the server they connect to (https://github.com/owncloud/enterprise/issues/3464).
• Since we have "Advanced Sharing Permissions" (10.2) server extensions may add permissions to user/group sharing. Implementing those in the clients has the same challenges as above.

This is also necessary for Android (owncloud/android#2667) and iOS (owncloud/ios-app#506).

[michaelstingl]

"Hybrid approach" would be still a viable alternative:

• Make "open owncloud in browser" log on automatically #633
• Make it possible to request an auth token (nonce) core#5453

[ogoffart]

Note that there is a POC for the hybrid approach:
#7564

[michaelstingl]

Replaced by:

• Open the browser instead of the share dialog #10241