feat(federation): seal federation peer client keys at rest (FED-M2-05) (#495)

apps/gateway/src/federation/peer-key.util.ts

@@ -0,0 +1,9 @@
+import { seal, unseal } from '@mosaicstack/auth';
+
+export function sealClientKey(privateKeyPem: string): string {
+  return seal(privateKeyPem);
+}
+
+export function unsealClientKey(sealedKey: string): string {
+  return unseal(sealedKey);
+}