add a new UAI to a existing Microsoft.ApiManagement/service

[scrocquesel-ml150]

In my use case, I want to be able to add user assigned identity on the apim management service from different biceps.

I tried with a sub module but I cannot just pass the identity property like Azure portal does when it PATCH the resource.

I come up with this submodule where I pass exiting value from the parent module and a resource existing.

param existingIdentity {
  type: string
  userAssignedIdentities: object
}
param name string
param serviceIdentityResourceId string

resource apimUpdate 'Microsoft.ApiManagement/service@2022-08-01' = {
  name: name
  identity: {
    type: existingIdentity.type == 'None' ? 'UserAssigned' : existingIdentity.type == 'SystemAssigned' ? 'SystemAssigned, UserAssigned' : existingIdentity.type == 'SystemAssigned, UserAssigned' ? 'SystemAssigned, UserAssigned' : 'UserAssigned'
    userAssignedIdentities: union(existingIdentity.userAssignedIdentities, {
        '${serviceIdentityResourceId}': {}
      })
  }
}

But I then must provide "properties", "sku" as they are required.

Could it be possible to just patch the resource without a deployment script ?