Route property must be named `url`

[Prokyonn]

Currently the SuluContentBundle forces the user to have the route property named url in the template.

This behaviour is not consistent throughout Sulu. The ArticleBundle did not force you to have to property named url usually it was called routePath.

Therefore migrating the ArticleBundle to the ContentBundle requires also a migration of the XML templates.

Possible solution

• Add the required steps to the UPGRADE.md.
• Add a MetadataListener that shows an error in the UI when an entity detail page is opened with a route property that is not named url.
• Force a url property in the template structure e.g.:

sulu_core:
    content:
        structure:
            required_properties:
                home:
                    - title
                    - url