D-12493: return 409 instead of 400 when entryId is not unique
D-12493: catch exception thrown when unique constraint is violated and return 409
D-12493: add more coverage in integration tests
Merge pull request #244 from mattkovacs/master

B-49312: Use Tomcat's Connection Pool
Merge pull request #243 from shintasmith/D-12493

return 409 instead of 400 when entryId is not unique
Fixing merge conflicts