I've been doing some exploration of the Power BI ARM REST API.
The endpoint https://management.azure.com/subscriptions/{subscriptionId}/providers/Microsoft.PowerBIDedicated/sku... referenced by https://docs.microsoft.com/en-us/rest/api/power-bi-embedded/capacities/listskus returns nothing. I have tried multiple subscriptionIds and I get a well-formed but ultimately empty JSON response.
I have also tried https://management.azure.com/providers/Microsoft.PowerBIDedicated/operations?api-version=2017-10-01 as indicated by https://docs.microsoft.com/en-us/rest/api/power-bi-embedded/operations/list
This returns the error "The resource type 'operations' could not be found in the namespace 'Microsoft.PowerBIDedicated' for api version '2017-10-01'. The supported api-versions are '2017-01-01-preview'.", so therefore your docs are buggy!
Replacing the api-version with 2017-01-01-preview does provoke a response - although the layout is a bit different to that specified by the docs.
