.NET Core solution that exemplify securing 2 app in Azure using the Managed Identity. This code is in .NET but the setup can be used for any programming language.
Tutorial: https://medium.com/@dtila/secure-web-api-services-in-azure-with-managed-identity-f1e5243be855
PowerShell script:
$tenantId = '<your tenant id>'
$serverRoleId = '7fbe8499-b22e-47e0-bc51-9c29bd1f40f2'
$clientManagedIdentity = '0f38730f-a246-415f-9edd-52c05292eeab'
$serverEnterpriseApp = '9014273b-4c34-4b58-ad1d-8ed04172d414'
Connect-AzureAd -TenantId $tenantId
New-AzureADServiceAppRoleAssignment `
-Id $serverRoleId `
-PrincipalId $clientManagedIdentity `
-ObjectId $clientManagedIdentity `
-ResourceId $serverEnterpriseApp