create attachment file table

backend/models/attachments.js

@@ -0,0 +1,26 @@
+function defineAttachment(sequelize, DataTypes) {
+  const Attachment = sequelize.define("Attachment", {
+    title: {
+      type: DataTypes.STRING,
+      allowNull: false,
+    },
+    detail: {
+      type: DataTypes.STRING,
+      allowNull: true,
+    },
+    path: {
+      type: DataTypes.STRING,
+      allowNull: false,
+    },
+  });
+
+  Attachment.associate = (models) => {
+    Attachment.belongsToMany(models.Case, {
+      through: "caseAttachments"
+    });
+  };
+
+  return Attachment;
+}
+
+module.exports = defineAttachment;