[BUG] Some improvements in error handling of Sharing feature

[jesmrec]

Change toast for snackbar

1. Remove device connection
2. Select to share an item with other user
3. Enter username of recipient

Current: Error message in a toast Expected: Error message in a snackbar (as every error all around the app)

Enforced password

1. In server dashboard, enforce password protection for any kind of permission
2. Create a public link, letting empty the (mandatory) password

Current: It was not posible to share this file or folder because server could not be reached Expected: Password mandatory, You must enter a password (or similar). Server responds with 404 and "message": "Cannot set the requested share permissions for...",

Privileges inheritance

1. User A shares an item with user B, only with sharing permissions (edition not granted)
2. User B shares with C, trying to grant edit permissions

Current: It was not possible to update this file or folder because it was not found Expected: Permissions error (or similar). Server responds with 404 and "message": "Cannot set the requested share permissions for...",

Privileges inheritance II

1. User A shares a folder with user B, only with sharing permissions (edition not granted)
2. User B creates a link over the folder with permission Download/View/Upload

Current: It was not possible to update this file or folder because it was not found Expected: Permissions error (or similar). Server responds with 404 and "message": "Cannot set the requested share permissions for...",

Password policy

1. In server, enable app Password Policy
2. Go to admin dashboard > Security and set a policy for links' passwords. For example, set 6 minimum characters and tick it.
3. Create a public link with a password length lower than 6 (or any other way that does not match the policy to force an error)

Current: It was not posible to share this file or folder because server could not be reached Expected: Password does not match the policy (or similar). Server responds 403 and "message": "The password is too short. At least 6 characters are required.",

Expiration policy

1. In server, enable app Password Policy
2. Go to admin dashboard > Security and set a policy for links' expiration. For example, set 7 days minimum until links expire if password is set and tick it.
3. Create a public link with a password and an expiration date later than 7 days.

Current: It was not posible to share this file or folder because server could not be reached Expected: Expiration does not match the policy (or similar). Server responds 403 and "message": "The expiration date cannot exceed 7 days.",