feat: updated backend for identity auth with reviewer optional

backend/src/db/migrations/20250321100157_k8s-self-reviewer-jwt.ts

@@ -0,0 +1,19 @@
+import { Knex } from "knex";
+
+import { TableName } from "../schemas";
+
+export async function up(knex: Knex): Promise<void> {
+  const hasReviewerJwtCol = await knex.schema.hasColumn(
+    TableName.IdentityKubernetesAuth,
+    "encryptedKubernetesTokenReviewerJwt"
+  );
+  if (hasReviewerJwtCol) {
+    await knex.schema.alterTable(TableName.IdentityKubernetesAuth, (t) => {
+      t.binary("encryptedKubernetesTokenReviewerJwt").nullable().alter();
+    });
+  }
+}
+
+export async function down(): Promise<void> {
+  // we can't make it back to non nullable, it will fail
+}