feat(account): send display name in account state to Core

The account state push carries displayName. It is published when the
name changes. Contract test updated.

src/test/resources/contract/auth-core-contract.json

@@ -37,12 +37,12 @@
     "applyStates": {
       "method": "POST",
       "path": "/internal/accounts/states",
-      "request": {"accounts": [{"userId": 42, "steamId": 76561198000000001, "blocked": true}]}
+      "request": {"accounts": [{"userId": 42, "steamId": 76561198000000001, "displayName": "lobo", "blocked": true}]}
     },
     "replaceStates": {
       "method": "PUT",
       "path": "/internal/accounts/states",
-      "request": {"accounts": [{"userId": 42, "steamId": null, "blocked": false}]}
+      "request": {"accounts": [{"userId": 42, "steamId": null, "displayName": "lobo", "blocked": false}]}
     },
     "purge": {
       "method": "POST",