chore: Allow omitting the default server secret from Helm installs

[ciarams87]

Proposed changes

Allow omitting the default server secret from Helm installs. If no kubernetes secret is defined for the default_server, the NGINX directive ssl_reject_handshake will be enabled for default_server. Currently, we try and create a secret for the default server if one is not provided, and will throw an error if the cert and key parameters are not provided. This change supports setting them to empty strings and omitting the CLI command if this is so.

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• [x] I have read the CONTRIBUTING doc
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] I have checked that all unit tests pass after adding my changes
• [x] I have updated necessary documentation
• [x] I have rebased my branch onto main
• [x] I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

[codecov-commenter]

Codecov Report

Merging #3087 (6350cb3) into main (17aad37) will decrease coverage by 0.01%. The diff coverage is n/a.

:exclamation: Current head 6350cb3 differs from pull request most recent head c45bd79. Consider uploading reports for the commit c45bd79 to get more accurate results

@@            Coverage Diff             @@
##             main    #3087      +/-   ##
==========================================
- Coverage   52.29%   52.28%   -0.02%     
==========================================
  Files          58       58              
  Lines       16006    16006              
==========================================
- Hits         8371     8369       -2     
- Misses       7356     7358       +2     
  Partials      279      279              

Impacted Files	Coverage Δ
...ternal/k8s/appprotect/app_protect_configuration.go	86.16% <0.00%> (-0.58%)	:arrow_down:

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