Base64URL needs to be more clearly specified

[decentralgabe]

The spec references the Base64URL format in a number of places. However, depending on the implementation there are some discrepancies in how encoding/decoding works.

According to RFC4648 padding may or may not be used. In section 3.2 there is a note on the unpadded implementation, sometimes referred to as a raw encoding.

The examples in the specification around long form DID use the version without padding. The spec language should be more specific to capture this nuance.