auth_active?/1 can check remote users and return true directly.

user: use pattern matching to determine if user is local or remote instead of the previous hairy logic

Will work for missing users and badly migrated users.

because of user refetch, accounts can stop existing (get_from_ap_id() can fail), accordingly
filter the follow requests for these failures.

(<nick>@<our_instance_host>).

These are all names that are used for domain.com/:route routes or projected to be.

[#114] Allowed unconfirmed users to authenticate if :account_activation_required is disabled prior to confirmation.
Ensured that no confirmation emails are sent if :account_activation_required is not true. Adjusted tests.

Added tests for `confirm_email` action.

unless requested by admin or moderator.

for registration, authentication, email confirmation, confirmation resending.
Made admin methods create confirmed users.

Introduced User.register/1 to encapsulate User record creation and post-registration actions.

[#114] Account confirmation email, registration as unconfirmed (config-based), auth prevention for unconfirmed.

Fixes #429.