Use v5/members instead of v3/members

[maxceem]

At the moment we are using "v3/members" endpoint to get users by the handle in 2 places, we have to update them to use "v5/members" instead.

[maxceem]

Done via #271

[maxceem]

QA guidelines:
This update would affect 2 features that we would have to verify (creating a payment and adding members to the team by handle):

• Create a WorkPeriodPayment. A challenge should be created with a winner listed correctly.
• Add 2 or more members to the team with one request. They should be added successfully.
• Add some non-existent members to the team - we should get a correct error that user(s) don't exist.

[sandhiyakavi]

@maxceem Tried Creating WorkPeriod Payment but both are still in Active status and not moved to "completed" status yet.Hence not able to check Winner listed.

WP Payment Ids: 4221b74a-38c3-43b2-99ca-e16e1e3ad359, 45e43570-435e-4db1-a351-a859d4ebd897
Challenge : https://www.topcoder-dev.com/challenges/ba6a5bbf-9907-404b-af69-a1ed8abf9e04
https://www.topcoder-dev.com/challenges/5701c582-3152-46e1-a0f2-04296b2cbd0f?tab=details

2. Added more members with handle/email id. Getting added successfully.
3. Getting correct user(s) don't exist error for invalid members

[sandhiyakavi]

@maxceem @nkumar-topcoder The challenge not moved to "completed" status was because of BA. It's moving to completed status now.

Winner detail is also updated in challenge api,

[sandhiyakavi]

Verified on Prod Env with @nkumar-topcoder .