Proposal: using URL and filename safe base64 encoder for serializing macaroons about libmacaroons

[rescrv]

I've got no objection to such a change. @rogpeppe, any objection to making this change in your implementation?

In any case, I suspect some decoders may just work with both formats, so we may be OK to change no matter what.

[rescrv]

I've gone ahead and implemented this in a backwards compatible way. New macaroons will be serialized in base64url, while the decoder can parse both old and new forms.

[nitram509]

👍
Followed with latest jmacaroons code :-)