Add xmlsec1 for django3-auth-saml2

[tim-schneider]

Related Issue: None

New Behavior

Extends requirements to enable the use of SAML SSO Providers via django3-auth-saml2.

As #876 has already introduced other libraries for Python Social Auth.

Contrast to Current Behavior

Currently these dependencies aren't included, meaning users can't take advantage of SAMLSSO by django3-auth-saml2 unless they create their own image.

Discussion: Benefits and Drawbacks

• Benefit: Enabling users to use functionality included in Netbox without needing to create bespoke images and SAML is more use than OICD in the enterprise world.
• Drawback: Additional dependencies increase the image size, and the version pinning will need to be periodically reviewed.
• Backwards-compatible: Yes

Changes to the Wiki

None

Proposed Release Note Entry

Requirements needed to use SAML SSO Providers via django3-auth-saml2 have been added

Double Check

• [x] I have read the comments and followed the PR template.
• [x] I have explained my PR according to the information in the comments.
• [x] My PR targets the develop branch.

[cimnine]

libxmlsec is already there in the list, isn't that enough?

[tim-schneider]

libxmlsec is already there in the list, isn't that enough?

Sadly not :(