openconnect: T6500: add support for multiple ca-certificates (backport #3682)

[mergify]

Change Summary

Add possibility to provide a full CA chain to the openconnect server.

• Support multiple CA certificates
• For every CA certificate specified, always determine the full certificate chain in the background and add the necessary SSL certificates

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Code style update (formatting, renaming)
• Refactoring (no functional changes)
• Migration from an old Vyatta component to vyos-1x, please link to related PR inside obsoleted component
• Other (please describe):

Related Task(s)

• https://vyos.dev/T6500

Related PR(s)

Component(s) name

openconnect

Proposed changes

How to test

Smoketest result

[email protected]:~$ /usr/libexec/vyos/tests/smoke/cli/test_vpn_openconnect.py
test_ocserv (__main__.TestVPNOpenConnect.test_ocserv) ... ok

----------------------------------------------------------------------
Ran 1 test in 12.664s

OK

Checklist:

• I have read the CONTRIBUTING document
• I have linked this PR to one or more Phabricator Task(s)
• I have run the components SMOKETESTS if applicable
• My commit headlines contain a valid Task id
• My change requires a change to the documentation
• I have updated the documentation accordingly

---

This is an automatic backport of pull request #3682 done by [Mergify](https://mergify.com).

[github-actions]

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