Alright folks, so here is the SilverStripe addon of the month:
https://github.com/sheadawson/silverstripe-linkable
Its the missing LinkField, you might look for.
There are some more addons for a LinkField out there, but this one is the best.
No wonder, the author is SilverStripe employee.
It features:
- external links
- link validation
- link a page from your site
- link a file from your assets
- oEmbed links
- the addon is translated, currently only for german, but add your own, its easy!