Refactor req.eventDetails parsing of GitHub web hook payload

[Ryanmtate]

Certain GitHub webhook events do not use the payload['action'] key for determining the sub action of the event. E.g.: https://github.com/git-token/reward-values/blob/11261646463b091b87da52beae46ba365e1a13bf/src/rewardValues.js#L9

Therefore, the eventDetails needs further control flow for parsing the different types of events.

webhook-manager/src/middleware/processRequest.js

Line 12 in cca4aa4

req.eventDetails = {