feat: make givenName and familyName optional

Drop them from the default human user schema's `required` array.
Profile fields are demo data — keeping them optional means a
minimal registration payload (email + password) still validates.

Author: vitorbari

api/openapi/endpoints/schemas/examples/default-human-user-schema.json

@@ -18,9 +18,7 @@
   },
   "required": [
     "email",
-    "password",
-    "givenName",
-    "familyName"
+    "password"
   ],
   "properties": {
     "email": {