I want to build a service where users can sign up (off-chain) to get credentials which give them the right to perform certain on-chain actions.
For example, lets pretend I'm building a service where someone can buy my time by holding my token (and burning it, or spending it or whatever), but I only want people who know me to be able to buy the token. So I have a site where my friends can give me their addresses, and then trading of my token will be restricted to within those addresses.
I want this list of valid owners to be updatable. How can I accomplish this?
For bonus points, lets assume the whitelist changes relatively frequently. Frequently enough that changing the contract becomes expensive. Is there a way around updating the contract itself?