Password (encrypted password with a salt generated from both domain and username values)
Application (use cases)
Signup: to create a new profile with empty list of logins
Adding new credentials
Removing exisiting credentials
Fetch a specific credentials by domain name and username
Search for multiple credentials by domain name
Presentation
For simplicity, I'm only considering CLI for now :')
But implementing a UI would be fairly simple because of the isolation of all layers and responsibilities.
Infrustructure
For the data storage implementation, I'm considering file storage (as json) and mysql one as well.
Via environment variables you can choose either or both implementations ;)