I'm interested in getting data (metadata and content of files) out of Microsoft Teams into my application using REST APIs. I have looked at Office 365 APIs and Graph APIs but, I could not find supporting documentation for Microsoft Teams.
Teams API is now added to beta endpoint in Microsoft Graph. In documentation, you can find it together with Groups. Post, Channel and Chat Thread are available. For example, documentation for "channel" resource is here: https://developer.microsoft.com/en-us/graph/docs/api-reference/beta/resources/channel