What do the parameters on the callback mean?

### Type of issue

Missing information

### Description

If I want to use OnChange to react to a change reported by the options monitor, I'd like to know what the parameters I'm being passed are for.

I'm guessing that the TOptions parameter is the previous options object prior to the changes that provoked the event, but I don't really know for sure. I don't know what data I'll get in the string.

### Page URL

https://learn.microsoft.com/en-us/dotnet/api/microsoft.extensions.options.ioptionsmonitor-1.onchange?view=net-8.0

### Content source URL

https://github.com/dotnet/dotnet-api-docs/blob/main/xml/Microsoft.Extensions.Options/IOptionsMonitor`1.xml

### Document Version Independent Id

162eb23c-646a-f261-fb19-70ec0096489d

### Article author

@dotnet-bot