Move error messages to string_view

using std::string_view on these lets us call them in more contexts, and
allows us to inline some previously more complex code.  In general, for
APIs like this, std::string_view should be preferred as it gives more
flexibility in calling conventions.

Tested:
curl --insecure "https://localhost:18080/redfish/v1/AccountService/Roles/foobar"                                                     ✔
{
  "error": {
    "@Message.ExtendedInfo": [
      {
        "@odata.type": "#Message.v1_1_1.Message",
        "Message": "The requested resource of type Role named 'foobar' was not found.",
        "MessageArgs": [
          "Role",
          "foobar"
        ],
        "MessageId": "Base.1.11.0.ResourceNotFound",
        "MessageSeverity": "Critical",
        "Resolution": "Provide a valid resource identifier and resubmit the request."
      }
    ],
    "code": "Base.1.11.0.ResourceNotFound",
    "message": "The requested resource of type Role named 'foobar' was not found."
  }
}

This is the same response as previously.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: I8ee17120c42d2a13677648c3395aa4f9ec2bd51a
diff --git a/redfish-core/lib/managers.hpp b/redfish-core/lib/managers.hpp
index a5e8c23..acaa40a 100644
--- a/redfish-core/lib/managers.hpp
+++ b/redfish-core/lib/managers.hpp
@@ -682,8 +682,7 @@
     if (config.empty())
     {
         BMCWEB_LOG_ERROR << "Empty Zones";
-        messages::propertyValueFormatError(response->res,
-                                           nlohmann::json::array(), "Zones");
+        messages::propertyValueFormatError(response->res, "[]", "Zones");
         return false;
     }
     for (auto& odata : config)
@@ -1601,8 +1600,8 @@
                 if (createNewObject && it.value() == nullptr)
                 {
                     // can't delete a non-existent object
-                    messages::propertyValueNotInList(response->res, it.value(),
-                                                     name);
+                    messages::propertyValueNotInList(response->res,
+                                                     it.value().dump(), name);
                     continue;
                 }