Signxml

- Allow cryptography versions >3 (but <4) (164)

- Add support for adding Signature Properties to a detached signature (160)

- Compare raw digest bytes instead of base64 encoded digests. Fixes 155

- Initial X509IssuerSerial/X509Digest support

- Support custom inclusive_ns_prefixes when signing

- Fix ECDSA signature encoding/decoding (150)

- Add InclusiveNamespaces PrefixList support for SignedInfo

- Test and documentation improvements

- Relax dependency version range on eight

- Update dependency installation documentation

- XMLSigner.sign(): add always_add_key_value kwarg to include both
X509Data and KeyValue for ill-defined signing applications

- XMLVerifier.verify(): reject signatures that contain both X509Data
and KeyValue by default; add ignore_ambiguous_key_info kwarg to
bypass

- Accept PEM keys as either str or bytes

- Drop defusedxml dependency; add security notes

- Add missing c14n transform for enveloping and detached methods (107)

- Relax pyOpenSSL dependency version range to include version 19

- Apply transforms and digest calculations to copies of root. Closes 125. (126)

- Documentation and test improvements