Removing code owners

[ssanadhya]

The Governance guidebook only talks about adding code-owners. We also need a way to trim the code owner list as contributors move out of the project. This proposal is to add the following section to the guidebook.

Removing code-owners

• An existing code-owner can always choose to leave the approvers-* team by sending a request to @wendallkaters .

• Periodically, each approvers-* team can also review the code owner activity and initiate a vote to remove a member from the team. @wendallkaters can facilitate the voting, similar to the process for becoming a code-owner. This should be done at least once every year.

[lucasgonze]

There should be a third bullet point for approvers-* teams that have no active members.

[maxhbr]

this was voted for and accepted on 2022-12-14

[Neudrino]

Implementation: https://github.com/magma/magma/wiki/Overview-of-the-Community-Structure-and-Governance#removing-code-owners

Please verify and close if sufficient. @ssanadhya @wendallkaters @maxhbr