DSND-3114: Add DeltaAt to DELETE endpoint header (#108) * Add delta at as request header for DELETE endpoint * Refactor delete service to take deltaAt as paremeter * Update service to check against request and existing deltaAt * Update service to process delete when resource does not exist * Add method to DateUtils to check stale deltas * Add conflict exception to handler * Refactor kafka api invocation to take ResourceChangedRequest document * Update unit and integrations tests * Add more unit tests to improve coverage * Removed unused method hasPscExemptions from service * Removed an usused import and reworded scenario * Refactor changes for readability and best practice * Moved PscStatementDocument from data-sync-api-sdk-java * Removed Optional wrapper from psc statement document in ResourceChangedRequest class * Moved ResourceChangedRequest mapping to separate class * Fixed unit/integration tests * Added test case for ResourceChangedRequestMapper * Added instant supplier to mapper to support testability * Optimised imports * Update dependencies * Update dependencies * Revert changes to Makefile * Upgrade parent pom version * Addressing PR comments * Fix error handling for kafka api call in service * Fix unit and intergration tests * Update pom to address vulnerability in spring-web * Added log map to an error log and removed unnecessary test * DSND-3114: Remove explicit type declaration