Audit logging - new schema (#20447)

* Audit logging - new schema added, old schema removed.

* fix linter error by running goimports

* Address review comments

* Address review comments

* Example usage of new audit logging API for the updateUserAuth call

* fixed unit test on auditing updating user record

* Changed the `TestUpdateConfigDiffInAuditRecord` testcase---it failed, because this PR changes how the `meta` field is serialized into the audit log records.

* fix linter error

api4/config_test.go

@@ -572,8 +572,9 @@ func TestUpdateConfigDiffInAuditRecord(t *testing.T) {
 	data, err := ioutil.ReadAll(logFile)
 	require.NoError(t, err)
 	require.NotEmpty(t, data)
+
 	require.Contains(t, string(data),
-		fmt.Sprintf(`"diff":"[{Path:ServiceSettings.ReadTimeout BaseVal:%d ActualVal:%d}]"`,
+		fmt.Sprintf(`"diff":[{"path":"ServiceSettings.ReadTimeout","base_val":%d,"actual_val":%d}]`,
 			timeoutVal, timeoutVal+1))
 }