Add current forging status to delegates/getActive endpoint

[reyraa]

Expected behaviour

We're displaying the delegate forging status in delegate monitor page. having this information, we can define a threshold for the number/percentage of not-forging active delegates and stay informed of any potential issues causing delegates fail to forge.

I think the status code should be provided in Api for two reason:

• The logics to interrogate data don't belong to client side application
• This way we prevent code duplication through different client applications

Actual behaviour

Presently the procedure of collecting this data is as below:

• in Api delegates/getActive provides the list of delegates
• in client the forgingStatus service performs some calculations to determine the forging status code
• in client the forgingStatus directive consumes that status code by performing a complex switch/case calculation to determine the status colour and icon to display in Delegate monitor page.

Which version this issue is opened against?

• Lisk Core version 0.9.x
• Lisk Explorer version 1.4.1