[GH-240] Add support for Microsoft National Clouds

[JoKneeMo]

Summary

This PR addresses #240 to add support for Microsoft National Cloud endpoints.
For my purposes I needed to connect with Microsoft GCC High.

I've added a new config item to select an Azure/Entra ID tenant type with support for Commercial, GCC/GCCH, US Gov (DoD), and China endpoints.

To address the login URLs, I overrode the oauth2/microsoft package to accept the tenant type config entry and return the proper endpoint.

Addressing the MS Graph API endpoints was a little more challenging.
The msgraph module was very out of date and did not support the SetURL function added 4 years ago.
That was added to the module to override the default url of graph.microsoft.com.
The MSGraph endpoint is controlled using the same new config item and returns the proper graph url.
The tokens used by graph are not cross cloud compatible.

I'm unsure of how to write the unit test mockups in this repo.

Additional Information

This logic could also be applied to the mattermost-plugin-msteams plugin and would address mattermost/mattermost-plugin-msteams#514. However, that issue is not marked as Help Wanted for community contribution. I'd be happy to open a PR for that one too otherwise I will wait for Mattermost Support to resolve it.

Ticket Link

Fixes #240

UI Screenshot

[mattermost-build]

Hello @JoKneeMo,

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[wiggin77]

@spirosoik can you assign someone from your team (or yourself) to look at this from an operations perspective?

[raghavaggarwal2308]

@JoKneeMo Can you please fix the failing CI and conflicts?