Finish preliminary backend endpoints / db structure for k8s auth

backend/src/services/identity-kubernetes-auth/identity-kubernetes-auth-fns.ts

@@ -0,0 +1,15 @@
+/**
+ * Extracts the K8s service account name and namespace
+ * from the username in this format: system:serviceaccount:default:infisical-auth
+ */
+export const extractK8sUsername = (username: string) => {
+  const parts = username.split(":");
+  // Ensure that the username format is correct
+  if (parts.length === 4 && parts[0] === "system" && parts[1] === "serviceaccount") {
+    return {
+      namespace: parts[2],
+      name: parts[3]
+    };
+  }
+  throw new Error("Invalid username format");
+};