FLN-344 NLv3 api: expose list id via the get list endpoint

# Purpose of Merge:

https://jira.sendgrid.net/browse/FLN-344
# PR - Merge Checklist:
-- Verify: 
- [x] Unit tests have passed
- [x] Code Review is done
- [ ] Dependent changes deployed

# Deps:
https://github.com/sendgrid/webapid/pull/70

# Risks:
n/a

# Rollback Process:
n/a