Improve loading of challenge under the milestone

[RishiRajSahu]

Currently we are making individual call to challenge api in order to load all challenges for a milestone. We would need to improve that by creating a new endpoint under challenge api which could result in getting all challenges for a milestoneId.

for eg - https://api.topcoder.com/v5/challenges?sortBy=updated&sortOrder=desc&projectId=28454&status=Active&page=1&perPage=50

For this we would have to add the milestoneId at root of challenge Object.
Open Question : how to handle the challenges which are already added to milestone objects on projects app side but didn't had milestoneId field for challenge object.

fyi @elkhawajah

[elkhawajah]

If we are adding milestoneId to challenge object, then we no more need to store the challenge ids in the mielstone object.