For compatibility with #299

Thereby ensuring that the chart is visible during redemption

Apparently this is no longer required and throws a warning now

Instead of the "zkap_name" field in the provider config blob -- which
may not be present

As another criteria for determining whether ZKAPs are required. This may
not be necessary, however, since "ristretto-issuer-root-url" should also
(always?) be present.

Since zkap_unit_name and zkap_unit_multiplier should suffice for
modifying user-facing representation of ZKAPs

To prevent the ZKAPs/usage chart legend labels from being truncated.

This is out-of-date and will need to be re-added later/separately.