* 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
0c5c74904b