feat: add database storage backend (#1091)

Co-authored-by: Elias Schneider <login@eliasschneider.com>

backend/internal/model/storage.go

@@ -0,0 +1,17 @@
+package model
+
+import (
+	datatype "github.com/pocket-id/pocket-id/backend/internal/model/types"
+)
+
+type Storage struct {
+	Path      string `gorm:"primaryKey"`
+	Data      []byte
+	Size      int64
+	ModTime   datatype.DateTime
+	CreatedAt datatype.DateTime
+}
+
+func (Storage) TableName() string {
+	return "storage"
+}