Collaborators for all roles

Background

Councilors, workers and leads, if operated by a single membership as now, makes it difficult for more than one real world person to operate the role, and this is a problem. People get sick, go on vacation or may have some legitimate reason for why they will be temporarily, and perhaps for an unknown duration, unable to operate the role. For key roles, this could be a serious problem.

Proposal

For all roles above, allow the primary owner to associated up to low a fixed number of other members IDs (so just a BTreeSet in the appropriate entity really), which allows any member with their ID in this set to authenticate as the primary owner for all purposes except updating set of collaborators.

• Workers in a working group, including lead.
• Council members in the council.
• Channel owner.
• A member.

While in principle there are all sorts of good reasons to introduce more granular permissions specific to each type of activity (e.g. not to withdraw from channel account, or not to unstake as a worker), this is too much complexity for what we can justify at this stage.

Note: collaborators for channel owners have been added, so this is a good thing to review.

┆Issue is synchronized with this Asana task by Unito

Start by reviewing the existing collaborator implementation for channel owners, which the issue says has already been added. Then trace the entities for workers and leads, council members, and members; done means each supports a bounded collaborator-member-ID set, with collaborators authenticating as the primary owner except when updating that set.