Feat/userop s3 storage (#99)

* feat(audit): add S3 storage schema for UserOp events

* docs: add UserOp S3 storage format documentation

* test(audit): add S3 integration tests for UserOp events

* docs: update AUDIT_S3_FORMAT.md with UserOp storage schema

* docs: keep transaction lookups in description

* fix: remove duplicate UserOpEventWrapper, import from reader

Author: DeStefaniAndrei