Creates an instance of LastModifiedVersion that passes the given lastModified date through the
If-Unmodified-Since conditional headers provided by the client.
For better accuracy, use ETag instead.
Appends relevant headers to the builder.
If-Modified-Since logic: all dates should be before this date (truncated to seconds).
If-Unmodified-Since logic: all dates should not be before this date (truncated to seconds).