Make required fields configurable

[jomo]

For example, in NRW, only phone number or email address are required (§ 8 CoronaSchVO), not both. For the purpose of data reduction you shouldn't require both from a user when they aren't legally required to provide both.

You could add a configuration for each state and let businesses select which state they are legally bound to.

Some competitive apps also allow to select from a list of required field combinations, but this requires somewhat detailed legal knowledge from business owners and is prone to mistakes.