chore: Initial database scaffolding (#2)

* chore: Initial database scaffolding

This implements migrations and code generation for interfacing with a PostgreSQL database.

A dependency is added for the "postgres" binary on the host, but that seems like an acceptable requirement considering it's our primary database.

An in-memory database object can be created for simple cross-OS and fast testing.

* Run tests in CI

* Use Docker instead of binaries on the host

* Skip database tests on non-Linux operating systems

* chore: Add golangci-lint and codecov

* Use consistent file names

database/migrate.go

@@ -0,0 +1,48 @@
+package database
+
+import (
+	"context"
+	"database/sql"
+	"embed"
+	"errors"
+
+	"github.com/golang-migrate/migrate/v4"
+	"github.com/golang-migrate/migrate/v4/database/postgres"
+	"github.com/golang-migrate/migrate/v4/source/iofs"
+	"golang.org/x/xerrors"
+)
+
+//go:embed migrations/*.sql
+var migrations embed.FS
+
+// Migrate runs SQL migrations to ensure the database schema is up-to-date.
+func Migrate(ctx context.Context, dbName string, db *sql.DB) error {
+	sourceDriver, err := iofs.New(migrations, "migrations")
+	if err != nil {
+		return xerrors.Errorf("create iofs: %w", err)
+	}
+	dbDriver, err := postgres.WithInstance(db, &postgres.Config{})
+	if err != nil {
+		return xerrors.Errorf("wrap postgres connection: %w", err)
+	}
+	m, err := migrate.NewWithInstance("", sourceDriver, dbName, dbDriver)
+	if err != nil {
+		return xerrors.Errorf("migrate: %w", err)
+	}
+	err = m.Up()
+	if err != nil {
+		if errors.Is(err, migrate.ErrNoChange) {
+			// It's OK if no changes happened!
+			return nil
+		}
+		return xerrors.Errorf("up: %w", err)
+	}
+	srcErr, dbErr := m.Close()
+	if srcErr != nil {
+		return xerrors.Errorf("close source: %w", err)
+	}
+	if dbErr != nil {
+		return xerrors.Errorf("close database: %w", err)
+	}
+	return nil
+}