feat: Add ent-based sqlite3 storage

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

storage/ent/schema/keys.go

@@ -0,0 +1,44 @@
+package schema
+
+import (
+	"github.com/facebook/ent"
+	"github.com/facebook/ent/schema/field"
+	"gopkg.in/square/go-jose.v2"
+
+	"github.com/dexidp/dex/storage"
+)
+
+/* Original SQL table:
+create table keys
+(
+    id                text      not null  primary key,
+    verification_keys blob      not null,
+    signing_key       blob      not null,
+    signing_key_pub   blob      not null,
+    next_rotation     timestamp not null
+);
+*/
+
+// Keys holds the schema definition for the Keys entity.
+type Keys struct {
+	ent.Schema
+}
+
+// Fields of the Keys.
+func (Keys) Fields() []ent.Field {
+	return []ent.Field{
+		field.Text("id").
+			SchemaType(textSchema).
+			NotEmpty().
+			Unique(),
+		field.JSON("verification_keys", []storage.VerificationKey{}),
+		field.JSON("signing_key", jose.JSONWebKey{}),
+		field.JSON("signing_key_pub", jose.JSONWebKey{}),
+		field.Time("next_rotation"),
+	}
+}
+
+// Edges of the Keys.
+func (Keys) Edges() []ent.Edge {
+	return []ent.Edge{}
+}