Onboarding Redirects depending on start URL

[SathyaJayabal]

https://topcoder.atlassian.net/browse/PLAT-320
Anyone registering for Topcoder anywhere outside of direct reg button, home page, or learn page should probably go back to /home page but those coming from challenge page should probably get redirected back to that page they started on as per the usual registration we used to have.

Example: If we are promoting a challenge and getting new registrants to come in and register via challenge or program page, they should be redirected back there and not to /home. they will then have to find that page again

[SathyaJayabal]

verified on dev
https://docs.google.com/spreadsheets/d/1TIDLE1J-K8wRFYAzIGsCIEYgtqJZDZ2rg7ClTOw4gec/edit#gid=1481278705

[SathyaJayabal]

verified on prod
https://docs.google.com/spreadsheets/d/1TIDLE1J-K8wRFYAzIGsCIEYgtqJZDZ2rg7ClTOw4gec/edit#gid=1481278705