You can use Microsoft Graph API which has some Microsoft Teams functionality like ‘Create Team’, ‘Delete Team’, ‘List Members’, ‘Add Member’.
Here is the documentation: Use the Microsoft Graph API to work with Microsoft Teams Maybe you can find what you desire there.
For widgets, I don’t thik there is one for Microsoft Teams.
There is a MS Teams connector in development as part of Mendix App Services. You can sign up for notifications when it’s available.
Microsoft Teams Connector
As Lenny posted, the way to achieve this currently is by using MS Graph API. There is a Mendix component available which may help you speed up development.
MS Graph Connector