feat: Add ent-based sqlite3 storage

Signed-off-by: m.nabokikh <maksim.nabokikh@flant.com>

storage/ent/sqlite.go

@@ -0,0 +1,65 @@
+package ent
+
+import (
+	"context"
+	"crypto/sha256"
+	"strings"
+
+	"github.com/facebook/ent/dialect/sql"
+
+	// Register sqlite driver.
+	_ "github.com/mattn/go-sqlite3"
+
+	"github.com/dexidp/dex/pkg/log"
+	"github.com/dexidp/dex/storage"
+	"github.com/dexidp/dex/storage/ent/client"
+	"github.com/dexidp/dex/storage/ent/db"
+)
+
+// SQLite3 options for creating an SQL db.
+type SQLite3 struct {
+	File string `json:"file"`
+}
+
+// Open always returns a new in sqlite3 storage.
+func (s *SQLite3) Open(logger log.Logger) (storage.Storage, error) {
+	logger.Debug("experimental ent-based storage driver is enabled")
+
+	// Implicitly set foreign_keys pragma to "on" because it is required by ent
+	s.File = addFK(s.File)
+
+	drv, err := sql.Open("sqlite3", s.File)
+	if err != nil {
+		return nil, err
+	}
+
+	pool := drv.DB()
+	if s.File == ":memory:" {
+		// sqlite3 uses file locks to coordinate concurrent access. In memory
+		// doesn't support this, so limit the number of connections to 1.
+		pool.SetMaxOpenConns(1)
+	}
+
+	databaseClient := client.NewDatabase(
+		client.WithClient(db.NewClient(db.Driver(drv))),
+		client.WithHasher(sha256.New),
+	)
+
+	if err := databaseClient.Schema().Create(context.TODO()); err != nil {
+		return nil, err
+	}
+
+	return databaseClient, nil
+}
+
+func addFK(dsn string) string {
+	if strings.Contains(dsn, "_fk") {
+		return dsn
+	}
+
+	delim := "?"
+	if strings.Contains(dsn, "?") {
+		delim = "&"
+	}
+	return dsn + delim + "_fk=1"
+}