Fix Version/s: None
ConnectionStringFactory does not support Oracle Wallet aliases nor can it handle situations where username exists but password does not.
Adding an `exists`method to DbAuth helps to avoid forcing the reading of username or passwords from db-auth.yaml config file and allows for other mechanisms to add that information at appropriate time.
- relates to
DM-18629 Add ability to select which schema should be used by Gen3 Butler
- Won't Fix
Jenskins #30440 passed, changes merged, ticket closed.