fix: Attachments should not always be deleted with their original document (#1715)

* fix: Attachments should not be deleted when their original document is deleted when referenced elsewhere

* fix: Attachments deleted prematurely when docs are placed in trash

* mock

* restore hook, cascading delete was the issue

server/migrations/20201211080408-attachment-no-cascade.js

@@ -0,0 +1,37 @@
+const tableName = 'attachments';
+
+// because of this issue in Sequelize the foreign key constraint may be named differently depending
+// on when the previous migrations were ran https://github.com/sequelize/sequelize/pull/9890
+const constraintNames = ['attachments_documentId_fkey', 'attachments_foreign_idx'];
+
+module.exports = {
+  up: async (queryInterface, Sequelize) => {
+    let error;
+    for (const constraintName of constraintNames) {
+      try {
+        await queryInterface.sequelize.query(`alter table "${tableName}" drop constraint "${constraintName}"`)
+        return;
+      } catch (err) {
+        error = err;
+      }
+    }
+    throw error;
+  },
+
+  down: async (queryInterface, Sequelize) => {
+    let error;
+    for (const constraintName of constraintNames) {
+      try {
+        await queryInterface.sequelize.query(
+          `alter table "${tableName}"
+            add constraint "${constraintName}" foreign key("documentId") references "documents" ("id")
+            on delete cascade`
+        );
+        return;
+      } catch (err) {
+        error = err;
+      }
+    }
+    throw error;
+  },
+};