Fix LDAP login page by using internal static resources rather than ex…

[fmartinou]

• Breaking change?

What changes did you make? (Give an overview)
The LDAP login page was loading css (bootstrap and signin from external CDN instead of using the local resources).
It already has been fixed for the Basic Auth login page but not the LDAP login page.

How Has This Been Tested?

• No need to
• Manually (please, describe, if necessary)
• Unit checks
• Integration checks
• Covered by existing automation

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (e.g. ENVIRONMENT VARIABLES)
• My changes generate no new warnings (e.g. Sonar is happy)
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged

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[github-actions]

Hello there fmartinou! 👋

Thank you and congrats 🎉 for opening your first PR on this project! ✨ 💖

We will try to review it soon!