RawDecode function decodes the input byte slice from a base64 URL-safe
encoded byte slice. It replaces the URL-unsafe characters with their
standard base64 counterparts and then decodes the result using the raw
standard base64 decoding.
RawEncode function encodes the input byte slice into a base64 URL-safe
encoded byte slice. It encodes the input using the raw standard base64
encoding and then replaces the URL-unsafe characters.