Creating a document provider to integrate with Microsoft Teams

I am looking at wanting to create a custom storage/document provider to integrate with Microsoft Teams.

I have looked through the code samples here but cannot find anything that would do this.

https://docs.microsoft.com/en-us/microsoftteams/platform/tutorials/code-samples

Looking at this link, it quotes:

"You can always add more cloud storage from other services. Additional services and integrations are available under the “Apps” menu, which you can access by clicking the “Apps” icon in the bottom-left corner"

This would suggest to me that you can build third party document providers, but without any documentation or examples I am stumped on how to do this.

https://www.howtogeek.com/661374/how-to-add-third-party-cloud-storage-in-microsoft-teams

Any help would be appreciated