fix(Approval Workflows): Workflows keep approval history after deletion (#2834)

* improvement: Approval Workflows can be deleted while maintaining history
Co-authored-by: Daniel Hougaard <daniel@infisical.com>

backend/src/db/migrations/20241203165840_allow-disabling-approval-workflows.ts

@@ -0,0 +1,59 @@
+import { Knex } from "knex";
+
+import { TableName } from "../schemas";
+
+export async function up(knex: Knex): Promise<void> {
+  const hasAccessApprovalPolicyDeletedAtColumn = await knex.schema.hasColumn(
+    TableName.AccessApprovalPolicy,
+    "deletedAt"
+  );
+  const hasSecretApprovalPolicyDeletedAtColumn = await knex.schema.hasColumn(
+    TableName.SecretApprovalPolicy,
+    "deletedAt"
+  );
+
+  if (!hasAccessApprovalPolicyDeletedAtColumn) {
+    await knex.schema.alterTable(TableName.AccessApprovalPolicy, (t) => {
+      t.timestamp("deletedAt");
+    });
+  }
+  if (!hasSecretApprovalPolicyDeletedAtColumn) {
+    await knex.schema.alterTable(TableName.SecretApprovalPolicy, (t) => {
+      t.timestamp("deletedAt");
+    });
+  }
+
+  await knex.schema.alterTable(TableName.AccessApprovalRequest, (t) => {
+    t.dropForeign(["privilegeId"]);
+
+    // Add the new foreign key constraint with ON DELETE SET NULL
+    t.foreign("privilegeId").references("id").inTable(TableName.ProjectUserAdditionalPrivilege).onDelete("SET NULL");
+  });
+}
+
+export async function down(knex: Knex): Promise<void> {
+  const hasAccessApprovalPolicyDeletedAtColumn = await knex.schema.hasColumn(
+    TableName.AccessApprovalPolicy,
+    "deletedAt"
+  );
+  const hasSecretApprovalPolicyDeletedAtColumn = await knex.schema.hasColumn(
+    TableName.SecretApprovalPolicy,
+    "deletedAt"
+  );
+
+  if (hasAccessApprovalPolicyDeletedAtColumn) {
+    await knex.schema.alterTable(TableName.AccessApprovalPolicy, (t) => {
+      t.dropColumn("deletedAt");
+    });
+  }
+  if (hasSecretApprovalPolicyDeletedAtColumn) {
+    await knex.schema.alterTable(TableName.SecretApprovalPolicy, (t) => {
+      t.dropColumn("deletedAt");
+    });
+  }
+
+  await knex.schema.alterTable(TableName.AccessApprovalRequest, (t) => {
+    t.dropForeign(["privilegeId"]);
+    t.foreign("privilegeId").references("id").inTable(TableName.ProjectUserAdditionalPrivilege).onDelete("CASCADE");
+  });
+}