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/postgres/postgres_test.go

@@ -0,0 +1,32 @@
+//go:build linux
+
+package postgres_test
+
+import (
+	"database/sql"
+	"testing"
+
+	"github.com/coder/coder/database/postgres"
+	"github.com/stretchr/testify/require"
+	"go.uber.org/goleak"
+
+	_ "github.com/lib/pq"
+)
+
+func TestMain(m *testing.M) {
+	goleak.VerifyTestMain(m)
+}
+
+func TestPostgres(t *testing.T) {
+	t.Parallel()
+
+	connect, close, err := postgres.Open()
+	require.NoError(t, err)
+	defer close()
+	db, err := sql.Open("postgres", connect)
+	require.NoError(t, err)
+	err = db.Ping()
+	require.NoError(t, err)
+	err = db.Close()
+	require.NoError(t, err)
+}