Enable Impersonation for SSRS reports on Azure

In our current Production Setup, we have setup SSRS and have been able to successfully use the SSRS reports in our .NET Web Application since years. We have used Impersonation in Web.Config (there might be other solutions available, we had to go with this) as shown below.

"true" userName="domainname/username" password="password">

This solution worked well becuase our Active Di rectory and SSRS server are located in the same Network / domain.

Now, as part of our Azure migration, we have migrated our SSRS server to an Azure VM. and we are able to view the reports using Report Server Manager within the VM. Now, when we access the Web Application (App Service - Web App), we are getting the following error. Below is the updated impersonation attribute that we have used.

"true" userName="[email protected]" password="password">

Could not create Windows user token from the credentials specified in the config file. Error from the operating system 'The user name or password is incorrect"

Obviously, this is because of the fact that we don't have a Active Directory domain setup in Azure. Below are my questions.

Can we utilize the users available in the default Directory that gets created on Azure?
If yes, how do I specify the impersonization?

Please help

Thanks,

Prawin