Required use of labels and other UI strings in Auth Services

[tomcrane]

From @ksclarke in Slack:

From the properties table at https://iiif.io/api/auth/1.0/#service-description it looks like label is required. But once one gets down to the Kiosk and External patterns we see:

There is no user interaction before opening the access cookie service URI, and therefore any of the label, header, description and confirmLabel properties are ignored if present.

The JSON examples have label and the other recommended but ignored properties. What's the point of making label required (and the others recommended) if the clients are instructed to ignore it/them?

@id for instance has a description that prescribes use for particular types of services: It is required with the Login, Clickthrough, or Kiosk patterns, in which the client opens the URI in order to obtain an access cookie.

[tomcrane]

For Auth 2, the presence of these fields in the examples is now confined to the interactive profile example.

Further, in b0e1101, text has been added to the table to qualify use of these properties.

[tomcrane]

Included in #2127

[zimeon]

Resolved. In Auth 2.0 the additional labels are defined only for the active interaction pattern: https://iiif.io/api/auth/2.0/#active-interaction-pattern