Graph API to create Tab in MS Teams with custom SPFx WebPart

Not really a great solution, but we have found that if you do not pass in a configuration but only provide the displayName and binding property in the JSON body, the tab is created with a "Set up" button that the user then needs to click to finish provisioning the tab: 

{
  "displayName": "My Custom Tab", 
  "teamsApp@odata.bind" : "<a href="<a href="https://graph.microsoft.com/v1.0/appCatalogs/teamsApps/xxxxx-yyyy-wwww-vvvv-1234567890" target="_blank">https://graph.microsoft.com/v1.0/appCatalogs/teamsApps/xxxxx-yyyy-wwww-vvvv-1234567890</a>" target="_blank"><a href="https://graph.microsoft.com/v1.0/appCatalogs/teamsApps/xxxxx-yyyy-wwww-vvvv-1234567890</a" target="_blank">https://graph.microsoft.com/v1.0/appCatalogs/teamsApps/xxxxx-yyyy-wwww-vvvv-1234567890</a</a>>"
}

Then, this is shown in the tab:

Clicking "Set up tab" gives this prompt: 

We also found that trying to add a tab to a team created with a Graph API call with a token with App Permissions would cause this to fail (show a broken icon rather than the Team icon) because the "General" folder was not created in the Team (until a user clicks the "Files" tab).  Creating the team with an access token with "Delegated Permissions" worked because the channel folder was set up properly (see https://techcommunity.microsoft.com/t5/teams-developer/adding-a-team-using-microsoft-graph-api-app-vs-delegated/td-p/1049694).

We are also still looking for a way to setup the tab for the user in advance, but at least this gets it to work.

Mary