Add domain configuration

[rumdood]

Site should be domain aware to match ActivityPub expectations. This would also allow simpler locators, storing just the account alias instead of the full path.

Alternatively the search could be domain agnostic but only store the account alias without the domain so it would work regardless of domain.

[rumdood]

Still need to add the ability for the management API to accept a locator of just "someuser" and either have it append that to the locator record (e.g. turn "someuser" into "[email protected]" or need to change the webfinger request handler to strip out the domain from requests and assume all requests are for the current domain (probably the better option).