Authentication via managed identity for assign blueprint with rest api

[carlosdepp]

I have to assign a blueprint via Rest API

https://docs.microsoft.com/en-us/rest/api/blueprints/assignments/create-or-update#assignment-with-user-assigned-managed-identity-at-subscription-scope

How can I get token with managed identity? Managed Identity is like below:

{
"id": "/subscriptions/xxx-xxx-xxx/resourcegroups/xxxx/providers/Microsoft.ManagedIdentity/userAssignedIdentities/xxx",
"name": "xxx",
"type": "Microsoft.ManagedIdentity/userAssignedIdentities",
"location": "westeurope",
"tags": {},
"properties": {
"tenantId": "xxx",
"principalId": "xxx",
"clientId": "xxx"
}
}
The enterprise app that created with managed identity hasn't any client secret. How can I get token for assign the the blueprint via api?

Any advice would be appreciated.