feat: Add MsgLeaveGroup to group module

[aleem1314]

Description

Closes: #9657

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[aaronc]

The challenge we're going to run into here is how do we adjust the threshold in ThresholdDecisionPolicy. Seems like that's not resolved from #9657. Ideas @aleem1314 @blushi @AmauryM ? Maybe we choose to switch to a PercentageDecisionPolicy or there's a method on DecisionPolicy to handle &/or reject members leaving

[blushi]

The challenge we're going to run into here is how do we adjust the threshold in ThresholdDecisionPolicy. Seems like that's not resolved from #9657. Ideas @aleem1314 @blushi @AmauryM ? Maybe we choose to switch to a PercentageDecisionPolicy or there's a method on DecisionPolicy to handle &/or reject members leaving

This issue could actually already happen when a group admin removes group members (through UpdateGroupMembers) and it's not currently handled... So I believe this should be addressed as a separate issue. I think a method on DecisionPolicy to reject members leaving if that would result in a conflict with its threshold (ie group.TotalWeight < policy.Threshold) could be a quick solution until we move to more flexible decision policies.

[blushi]

@aaronc Actually I've just realized that currently, you cannot create a proposal if the policy threshold is greater than the total group weight, see

cosmos-sdk/x/group/keeper/msg_server.go

Line 416 in aaa61e3

err = policy.Validate(g)

and

cosmos-sdk/x/group/types.go

Lines 115 to 117 in aaa61e3

	if threshold.Cmp(totalWeight) > 0 {
	return sdkerrors.Wrap(errors.ErrInvalid, "policy threshold should not be greater than the total group weight")
	}

So in this case, current proposals get invalidated (because group is updated) and new proposals can't be created.

But I agree this is not ideal from a user standpoint, this should error earlier on members updates rather than on proposal creation, thoughts?

[codecov]

Codecov Report

Merging #10887 (a4bfd0c) into master (489b399) will decrease coverage by 0.02%.
The diff coverage is 82.28%.

@@            Coverage Diff             @@
##           master   #10887      +/-   ##
==========================================
- Coverage   66.02%   66.00%   -0.03%     
==========================================
  Files         704      665      -39     
  Lines       71853    69032    -2821     
==========================================
- Hits        47442    45562    -1880     
+ Misses      21472    20799     -673     
+ Partials     2939     2671     -268     

Impacted Files	Coverage Δ
client/flags/flags.go	20.68% <ø> (+0.35%)	⬆️
client/tx/factory.go	26.08% <0.00%> (-0.12%)	⬇️
x/auth/client/cli/tips.go	0.00% <0.00%> (ø)
x/group/codec.go	43.47% <50.00%> (+0.29%)	⬆️
x/group/msgs.go	53.87% <52.63%> (-0.05%)	⬇️
x/group/keeper/msg_server.go	71.92% <62.26%> (-0.78%)	⬇️
x/group/simulation/operations.go	66.92% <66.66%> (+0.05%)	⬆️
x/group/client/testutil/tx.go	99.77% <99.43%> (-0.03%)	⬇️
x/auth/client/testutil/suite.go	97.50% <100.00%> (+0.17%)	⬆️
orm/encoding/ormkv/seq.go
... and 42 more

[lgtm-com]

This pull request introduces 1 alert when merging d877e54 into eb01537 - view on LGTM.com

new alerts:

• 1 for Useless assignment to local variable

[lgtm-com]

This pull request introduces 1 alert when merging 90306c1 into 6ea2049 - view on LGTM.com

new alerts:

• 1 for Useless assignment to local variable

[lgtm-com]

This pull request introduces 1 alert when merging cce7b03 into 6ea2049 - view on LGTM.com

new alerts:

• 1 for Useless assignment to local variable

[lgtm-com]

This pull request introduces 1 alert when merging 8f9bfb6 into 96bc6a5 - view on LGTM.com

new alerts:

• 1 for Useless assignment to local variable

[amaury1093]

LGTM

[blushi]

Pre-approving