refactor: restructure modules

[StewartJingga]

Changes:
bump go version from 1.13 to 1.16.

Restructured packages

1. split models package into record, lineage and discovery.
2. lineage and discovery are depending on record.
3. record package is responsible for defining a record and storing.
4. record package has context on tags and ownership as they are part of record's metadata.
5. record package does not have context on lineage and discovery.