Python xmlsec library support

[AndrewFoxUUID]

Description

The feature or problem addressed by this PR

What your changes do and why you chose this solution

Checklist

• Checked that no other issues or pull requests exist for the same issue/change
• Added tests covering the new functionality
• Updated documentation OR the change is too minor to be documented
• Updated CHANGELOG.md OR changes are insignificant

[c00kiemon5ter]

Hello and thank you for this contribution. I'd like to suggest to make the changes on their own class as a new crypto backend, to keep the new functionality clean.
Or, is the intention to use XMLSecurity and the xmlsec module along side each other?

[AndrewFoxUUID]

Hello and thank you for this contribution. I'd like to suggest to make the changes on their own class as a new crypto backend, to keep the new functionality clean. Or, is the intention to use XMLSecurity and the xmlsec module along side each other?

My understanding of the current codebase is that the XmlSecurityBackend is already using xmlsec, it just hasn't been updated to use xmlsec's newest functionalities, and isn't nearly as developed as the XmlSec1 backend. The main purpose of these changes is to use xmlsec instead of creating a terminal flow to execute a libxmlsec1 call for better efficiency.

[af-splashtop-test]

@c00kiemon5ter 654151 Can you please review these changes?