fix: RetrievePdsDemographic API to return PdsDemographic objects instead of ParticipantDemographic#1462

SamAinsworth-NHS merged 7 commits intomainNHSDigital/dtos-cohort-manager:mainfrom

Fix/retrieve-pds-demo-to-demographic-responseNHSDigital/dtos-cohort-manager:Fix/retrieve-pds-demo-to-demographic-responseCopy head branch name to clipboard