This commit is part of a refactor that unifies configuration of the
sqldb and kvdb packages for SQL backends.
In order to unify the SQLite and Postgres configuration under sqldb we
first need to ensure that the final config types are compatible with
the alreay deployed versions.
This commit provides the scaffolding for using the new sql stores.
The new interfaces, structs and methods are in sync with other projects
like Taproot Assets.
- Transactional Queries: the sqldb package defines the interfaces required
to execute transactional queries to our storage interface.
- Migration Files Embedded: the migration files are embedded into the binary.
- Database Migrations: I kept the use of 'golang-migrate' to ensure our
codebase remains in sync with the other projects, but can be changed.
- Build Flags for Conditional DB Target: flexibility to specify our database
target at compile-time based on the build flags in the same way we do
with our kv stores.
- Update modules: ran `go mod tidy`.
