Support a user-friendly name property to attributes

In order to properly render pages dynamically, administrators should be able to set the display name of an attribute. This property should make it possible to render paged dynamically where the name of the attribute should be different than its internal name.

IMO, it makes more sense to introduce the display name as a top-level attribute property as follows:

{
    "name": "birthdate"
    "displayName": "Date of Birth"
}

Although annotations could be used for the same purpose, making it a top-level property makes it more explicit in the configuration schema as it is a very common configuration.

Another possible solution, although a bit different from other places in Keycloak, to define a default placeholder for display name as follows: realm_name.user.profile.attribute_name.

Regardless, we need i18n.