feat: Add ent-based sqlite3 storage

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

storage/ent/schema/devicetoken.go

@@ -0,0 +1,45 @@
+package schema
+
+import (
+	"github.com/facebook/ent"
+	"github.com/facebook/ent/schema/field"
+)
+
+/* Original SQL table:
+create table device_token
+(
+    device_code   text      not null primary key,
+    status        text      not null,
+    token         blob,
+    expiry        timestamp not null,
+    last_request  timestamp not null,
+    poll_interval integer   not null
+);
+*/
+
+// DeviceToken holds the schema definition for the DeviceToken entity.
+type DeviceToken struct {
+	ent.Schema
+}
+
+// Fields of the DeviceToken.
+func (DeviceToken) Fields() []ent.Field {
+	return []ent.Field{
+		field.Text("device_code").
+			SchemaType(textSchema).
+			NotEmpty().
+			Unique(),
+		field.Text("status").
+			SchemaType(textSchema).
+			NotEmpty(),
+		field.Bytes("token").Nillable().Optional(),
+		field.Time("expiry"),
+		field.Time("last_request"),
+		field.Int("poll_interval"),
+	}
+}
+
+// Edges of the DeviceToken.
+func (DeviceToken) Edges() []ent.Edge {
+	return []ent.Edge{}
+}