The 'Story URL' field is required, but by default is in a collapsed tab.
Users stumble over this when they try to Save a story.
The problem is increased since the validation error might not be visible if the story is long( - but solving the validation message does not go far enough towards solving this problem.).

Another issue is that the name "URL" is misleading for the field. A URL is a full url - whereas this is just a piece of it. Depending on the pages that reference it - the directory path of the story might also be part of the url. Maybe we should consider renaming it to something like slug.

Specification decided by avongunten and czimmermann:

• Change label from "Story URL" to "URL slug"
• Change placeholder text from "Add URL" to "Add URL slug"
• URL slug field is not required
• On save: If the url slug field is empty, then set the name automatically based on the title the user enters.
• When you open the story again - that generated name should show in the field. The user can edit it.
• If the title is changed later, the name is not automatically changed.