New auth code doesn't work if multiple accounts are signed in or you sign in to an account with access to multiple tenants.

https://github.com/microsoft/vscode-azuretools/issues/1809 affects the new code for https://github.com/Azure/bicep/issues/14101, which should ship in December. If the bug isn't fixed before we ship, may need to work around it (I think I can at least detect the issue and ask them to sign out of one of them).

Start by reading the linked vscode-azuretools issue 1809 and Azure Bicep issue 14101 to understand the new authentication code and its tenant behavior. Reproduce the failure with multiple signed-in accounts or an account accessing multiple tenants, then confirm that authentication succeeds or that the documented workaround is triggered before the December release.

Written by the indexing model from the issue text.