Feature: Anonymous Usage of WIRE (with multiple user stories)

Feature

As a WIRE user (private and business)
i want to use WIRE fully anonymously
so that not even WIRE knows who i am.

Rationale
There are different scenarios why WIRE should offer an option for fully anonymous usage to protect its customers for abuse.

Threema / Proton / Mullvad already implemented this feature.

Different countries, different customs. Due to current political situations world-wide even the functionality of democratic governments are under test. Not even speaking about less democratic regimes. Which means that political interest can turn against normal citizens or companies quickly

In case of a breach on provider level or when a state actor tries to force WIRE to disclose user data, WIRE should retain less data as possible.

That implies the following user stories:

(1) Signup without email address
As a WIRE user i want to sign up without email address so that my WIRE user name is my only unique identifier.

I know that WIRE currently is not requiring phone numbers (like Signal) for Sign up, but it requires a email addresse.
That process is not providing extra security (KnowYourCustomer) for anybody. Its just an extra piece of information WIRE has from me which could be exploited. Since everybody could easily create an anonymous email addresse (e.g. proton via TOR) - requiring a email address for WIRE is a small inconvenience for the users. 

(2) Payment
As a WIRE user i want to pay anonymously (cash / crypto) so that my payment method can not be tracked.

(3) Invoicing
As a WIRE user i want to receive a tax deducible but generic invoice without my explicit (company) name so that my identify is not leaked on document level.

(4) Alias Usernames
As a WIRE user is want to use Alias usernames additional to my main user name so that i do now need to disclose my main username (e.g. Real Name) to all conversation partners.