Use an incremental group id when creating a group in contracts

[vplasencia]

Related Issue(s)

Closes #682

Checklist

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my code
• [x] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have run yarn prettier and yarn lint without getting any errors
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
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[openzeppelin-code[bot]]

Use an incremental group id when creating a group in contracts

Generated at commit: b12dd0fd984fa3d5de9f2c2bd17f1e470cd6f4d1

🚨 Report Summary

	Severity Level	Results
Contracts	Critical High Medium Low Note Total	0 0 0 4 16 20
Dependencies	Critical High Medium Low Note Total	0 0 0 0 0 0

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For more details view the full report in OpenZeppelin Code Inspector

[vplasencia]

Hey @cedoor I think that's a great idea, we could create a new issue. This will make it easier to use the function. There are a lot of cases where the admin is msg.sender.