Add new commandlet, Get-PnPExpiringMicrosoft365Groups

[koskila]

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https://github.com/pnp/powerShell/blob/dev/CONTRIBUTING.md

Type

• Bug Fix
• New Feature
• Sample

Related Issues?

None.

What is in this Pull Request ?

This PR adds new commandlet, Get-PnPExpiringMicrosoft365Groups. By default, it'll return groups expiring in the next 31 days (to be in line with SharePoint/OneDrive's retention period's 31-day months), but this can be changed by supplying a value to -Limit parameter.

I had to pass the additionalheaders to a few places to enable "advanced query capabilities", but I tried to comment that in the code to make it clear why.

Guidance

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[gautamdsheth]

Awesome stuff @koskila, really glad to have you contributing here 🙏😊

Couple of things:

1. Can you please use singular, i.e rename it to Get-PnPMicrosoft365ExpiringGroup? It is a PowerShell convention. I know it's a bit weird, but that's how it is :(

2. Can you also please add the documentation for this? You can create a Get-PnPMicrosoft365ExpiringGroup.md file inside the documentation folder. You can check other docs for example.

[gautamdsheth]

Thank you @koskila, have merged it !!