Trailing padding is required to be removed from base64url encoded keys. This is because RFC 7517 defines base64url the same as RFC 7515 Section 2:
- https://datatracker.ietf.org/doc/html/rfc7517#section-1.1
- https://datatracker.ietf.org/doc/html/rfc7515#section-2
with all trailing '=' characters omitted
However, not all JWKS are perfectly RFC compliant and some include trailing = characters for their base64url encoding. These non-RFC compliant JWKS implementations will be supported since it's trivial to support the removal of trailing = client side and will not impact performance in any noticeable way.