Accept databaseId for Firestore

As of July 2023, [a project can have multiple Firebase databases associated with it](https://cloud.google.com/blog/products/databases/manage-multiple-firestore-databases-in-a-project). The corresponding Terraform code can be updated to create a uniquely named Firestore database, however the application code must be updated to allow specifying a database ID other than the default. This will simplify deployment and allow for multiple and separate dev journey deployments in a single project.