feat: pass args to task onSuccess and onFail callbacks

[slavanossar]

What?

Passes the same args provided to a task's shouldRestore function to both the onSuccess & onFail callbacks

Why?

Currently onSuccess and onFail are quite useless without any context, this will allow for a wider range of functionality:

• Checking if it's the last failure
• Access to the task input
• Access to req to allow logging, email notifications, etc.

How?

1. Created a new TaskCallbackArgs type, which replicates the args of the ShouldRestoreFn type.
2. Add a TaskCallbackFn type
3. Update the function calls of both onSuccess and onFail.

Questions

• I wasn't sure about the typing of input – I can see input: input! being used elsewhere for task errors so I replicated that.
• Same for taskStatus, I added a type check but I'm not sure if this is the right approach (what would scenario would result in a null value?). Should TaskCallbackArgs['taskStatus'] be typed to allow for null values?