Handle duplicate members in cw4-group create

[codehans]

When a cw4-group contract is instantiated with a list of members where some are duplicated, the iterator overwrites any previous member weight, whilst still incrementing the total weight. This PR merges duplicate weights in the create function

[CLAassistant]

All committers have signed the CLA.

[ueco-jb]

@codehans will you pick up that PR and add some proper test?

[0xekez]

fwiw - i do think this could be considered to be a non-backwards compatible change.

for example, before our audit (see the first issue there) we did not dedup the members list when instantiating a dao that uses cw4-groups. we now do, but were this to land we'd probably stop doing that to be consistent with the new behavior.

[codehans]

apologies @ueco-jb @ezekiiel missed this one. this isn't something we're actively using or particularly precious about. happy to leave as-is, especially as time is fairly scarce these days

[uint]

This looks like a serious flaw. If you don't mind, I'll pick this up, rebase, add a test, and merge. @codehans do you mind if I push here?

[uint]

fwiw - i do think this could be considered to be a non-backwards compatible change.

@0xekez That's fair! I don't think we guarantee backwards-compatibility currently (0.* semantic versions). Is this going to cause problems for you?

[codehans]

This looks like a serious flaw. If you don't mind, I'll pick this up, rebase, add a test, and merge. @codehans do you mind if I push here?

go ahead!

[uint]

@codehans Would you mind signing the CLA thing? I'll need that to merge later.

[uint]

Actually, I'm going to have duplicate entries throw an error since it's not clear what outcome the user expected. As things stand, this PR would cause instantiation and ExecuteMsg::UpdateMembers to have inconsistent behavior.

[ethanfrey]

lgtm with error on duplicates