UrlSafe
The "base64url" encoding specified by RFC 4648 section 5
, Base 64 Encoding with URL and Filename Safe Alphabet.
Uses "The URL and Filename safe Base 64 Alphabet" as specified in Table 2 of RFC 4648 for encoding and decoding. Encode operation does not add any line separator character. Decode operation throws if it encounters a character outside the base64url alphabet.
The character '='
is used for padding.