Add Group Module

[aaronc]

Summary

Add group module to the Cosmos SDK. (Part of #7074)

Problem Definition

In #5236 it was proposed that the group module live outside of the SDK maintained by Regen Network in our own fork of cosmos-modules. That is where it currently lives: https://github.com/regen-network/regen-ledger/tree/marie/136-x-group/x/group

The main rationale for this decision was lack of bandwidth on the SDK team to support this module. This is no longer an immediate problem as the Regen team is now one of the principle maintainers of the SDK.

Nevertheless, our team also believes in a tightly scoped SDK and growing the ecosystem of modules around the SDK (#7421) so this is not a sufficient reason on its own.

The biggest motivations for including the group module in the SDK are:

• the amount of community enthusiasm around this module being a core part of "cosmos" and included in gaia, and
• in particular the desire of the ICF to focus on governance as a primary theme for 2021 and in particular the idea that on-chain governance would involve sub-committees - possibly managed by the group module

It was even discussed in some conversations that there could be some convergence of the group module and x/gov as both support proposals and voting simply with different underlying methods (fixed weights vs delegated stake).

If there is to be some integration of the group module into on-chain governance, it will be much easier to do this work within the SDK.

Proposal

We propose merging the group module in https://github.com/regen-network/cosmos-modules/tree/master/incubator/group with its supporting ORM/Table Store package (#7098) into the Cosmos SDK and continuing development here. This would include adding ADRs for both pieces.

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[clevinson]

Strongly in favor of this.

Also, worth noting that group module is an important part of our strategy for improved key management (key rotation, on-chain multi-sig accounts), which gets a lot of attention in the SDK community as well.

[aaronc]

/cc @okwme @hxrts

[hxrts]

Definitely onboard with this. I think it will also encourage community feedback on the groups module design as well.

Do you think there will be particular groups features that some chains will want disabled? I can't think of any offhand, but if so we should try to make this straightforward for devs.