Support ERC-173

[RenanSouza2]

Motivation

There's an open PR for supporting ERC173, and AccessControlDefaultAdminRules.sol imports IERC5313, maybe Ownable should do the same.

[ernestognw]

Hey @RenanSouza2, we're already considering this for 5.0 and there's an open PR (#2874) but using ERC173 instead. We didn't implement it before because there was some discussion around keeping backwards compatibility in the transferOwnership function (note it allows renouncing by transferring ownership to the address 0).

I couldn't find any issue for specifically discussing this so I'll rename this issue since #2874 is pretty old.

It's something we might be interested in guiding a contributor to implement.

[ernestognw]

Some questions we might need to consider:

• Shall we support IERC5313 in certain cases other than AccessControlDefaultAdminRules?
• How does this apply to Ownable2Step?

[RenanSouza2]

I like ERC5313 more because ERC173 suggests the use of ERC165

Ownable2Step would already inherit the changes, should something else be done here?

[Amxx]

Ownable already support ERC5313 (which is only about the owner() getter).

The main point of supporting ERC-173 is enabling ownership transfers to address(0) using the "normal" transferOwnership function. Currently we forbid that, and have the renounceOwnerhip function instead.