Clarity on whether or not padding is required while Base64URL Encoding

[MichaelJBRichards]

I suggest that we should add the following wording to ensure that the requirement for padding is clear.

In section 3 (the API Signature Definition) of the Signature document: "For the avoidance of doubt: whenever reference is made to Base64URL encoding in the signature definition or in the examples included in this document, then the encoding MUST include appropriate pad characters as specified in Section 3.2 of RFC 4648 (https://tools.ietf.org/html/rfc4648#section-3.2)"

In section 7.2.17 (the definition of a BinaryString) of the Open API specification: "For the avoidance of doubt: the Base64URL encoding for a BinaryString MUST include appropriate pad characters as specified in Section 3.2 of RFC 4648 (https://tools.ietf.org/html/rfc4648#section-3.2)"