Remove commons-codec dependency

[JonathanGiles]

it's only used in three places for encoding to base64.

[henrik-me]

Jonathan Giles (@JonathanGiles) : what is your recommendation instead? Just ensuring we don't do it differently from what you expect.

[JonathanGiles]

In the first instance you should consider using the Java 8 java.util.Base64 class. There is a good tutorial here: https://www.baeldung.com/java-base64-encode-and-decode

If that is not sufficient, we should explore options, but probably writing out an implementation of the one method that was being used (if I recall correctly) might be the next-best option.