There doesn't seem to be any way to use REST API calls to produce Availability SLA report similar to the GUI method (containing daily Availability history and business hours). Is there a way to produce and export these reports using automation?

I am using /reports/availability_summary/{monitor_id}?period=7

Additionally, JSON output from that call is flawed - it contains duplicate items ('totaldowntime' and 'TotalDownTime'), which conflict when used with Powershell:

ConvertFrom-Json : Cannot convert the JSON string because a dictionary that was converted from the string contains the duplicated keys 'totaldowntime' and 'TotalDownTime'.