Fix Challenge.platformId and Challenge.websiteUrl

[coveralls]

Pull Request Test Coverage Report for Build 1217818491

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 17 unchanged lines in 1 file lost coverage.
• Overall coverage remained the same at 46.463%

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Files with Coverage Reduction	New Missed Lines	%
openapi_server/controllers/challenge_controller.py	17	18.07%
<!--	Total:	17		-->

Totals
Change from base Build 1214692765:	0.0%
Covered Lines:	1143
Relevant Lines:	2460

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💛 - Coveralls