ENS registrar for user subdomains

[Ivshti]

The goal is to allow users to easily register an ENS subdomain through their Identity contracts.

This would not require any changes to the Identity, as execute can be used to trigger the name registrarion; it would simply require a registrar that will be set for adex.eth:

https://github.com/ensdomains/ens/blob/master/contracts/FIFSRegistrar.sol

See this as an example of what the Identity will do, once the user decides to register a username: https://github.com/UniversalLogin/UniversalLoginSDK/blob/master/universal-login-contracts/contracts/utils/ENSUtils.sol

Unlike the Universal login SDK, we won't force users into picking a username, it will be an entirely optional step that happens after registration

This is a simple task, but must be done within the team (hence no gitcoin-candidate) cause it requires nailing down a few important details; using a simple registrar won't be completely trustless, as we can change it at any time; to fix this, there must be a SC that owns the name completely; we will start with the simple FIFSRegistrar, and this could be an upgrade later down the line

a more trustless solution can be seen here: https://github.com/ensdomains/subdomain-registrar ; we won't use this, since we simply want a FIFSregistrar for our users

requirements:

• [x] inability to register names that are too short (they will be reserved) - will be controlled in the platform initially
• [x] certain level of upgradability so we can add shorter names later on - we can always update the controller
• [x] migration plan to a trustless setup (where the contract would own the adex.eth domain) - we can always update the controller

see also:

• https://docs.ens.domains/dapp-developer-guide/ens-enabling-your-dapp

[Ivshti]

This is done: https://etherscan.io/address/0xa3f69f48d4a45419d48b56b1cfbf4af2d4586728#code