feat(sharebymail): improve share email format

[skjnldsv]

Before	After

As discussed:

1. Removed » and «
2. Add expiration
3. Improve layout

Fix #15680
cc @jancborchardt @nimishavijay @marcoambrosini

[szaimen]

I just looked at the after screenshot and I was wondering if technically these elements could be bold?

Also, the button on the bottom should probably have the same border-radius that we are useing in Nextcloud for buttons?

cc @nextcloud/designers

[skjnldsv]

I just looked at the after screenshot and I was wondering if technically these elements could be bold?

• For Note and Expiration, the place to fix it is here. This will change for all apps using our email templating (like calendar events)
  
• For the folder title, that would be nice, but it's not supported for now
  We don't support custom html. We could add some custom support like ** to convert to bold during the template processing.
  But I'd say this is something for 31 or later

[skjnldsv]

Addressed the border radius, see first post

Two-button example:

[nimishavijay]

Super nice! Very cool that the buttons are rounded now :)

All looks good, only small change I would suggest is to remove the message in gray at the bottom "X shared Y with you. Click the button below to open it." as it seems redundant now :)

Approving to not block