MM-11262: database config store (#10281)

* vendor github.com/jmoiron/sqlx

* MM-11262: introduce a database store

* revert unnecessary fmt.Errorf

* simplify unit test helper methods

* remote TODO re: retry

* relocate initializeConfigurationsTable for clarity

* factor out a commonStore

* acquire database config lock on close for safety

* add missing header

* fix lock comment

config/main_test.go

@@ -1,17 +1,45 @@
-package config
+package config_test
 
 import (
-	"io"
+	"testing"
 
+	"github.com/go-sql-driver/mysql"
 	"github.com/mattermost/mattermost-server/model"
+	"github.com/mattermost/mattermost-server/testlib"
+	"github.com/stretchr/testify/require"
 )
 
-// MarshalConfig exposes the internal marshalConfig to tests only.
-func MarshalConfig(cfg *model.Config) ([]byte, error) {
-	return marshalConfig(cfg)
+var mainHelper *testlib.MainHelper
+
+func TestMain(m *testing.M) {
+	mainHelper = testlib.NewMainHelper()
+	defer mainHelper.Close()
+
+	mainHelper.Main(m)
 }
 
-// UnmarshalConfig exposes the internal unmarshalConfig to tests only.
-func UnmarshalConfig(r io.Reader, allowEnvironmentOverrides bool) (*model.Config, map[string]interface{}, error) {
-	return unmarshalConfig(r, allowEnvironmentOverrides)
+// truncateTables clears tables used by the config package for reuse in other tests
+func truncateTables(t *testing.T) {
+	t.Helper()
+
+	switch *mainHelper.Settings.DriverName {
+	case model.DATABASE_DRIVER_MYSQL:
+		_, err := mainHelper.SqlSupplier.GetMaster().Db.Exec("TRUNCATE TABLE Configurations")
+		if err != nil {
+			if driverErr, ok := err.(*mysql.MySQLError); ok {
+				// Ignore if the Configurations table does not exist.
+				if driverErr.Number == 1146 {
+					return
+				}
+			}
+		}
+		require.NoError(t, err)
+
+	case model.DATABASE_DRIVER_POSTGRES:
+		_, err := mainHelper.SqlSupplier.GetMaster().Db.Exec("TRUNCATE TABLE Configurations")
+		require.NoError(t, err)
+
+	default:
+		t.Fatalf("unsupported driver name: %s", *mainHelper.Settings.DriverName)
+	}
 }