added custom annotation to ingress for CORS

[jmozd]

Proposed changes

support CORS by providing a custom annotation to Ingress', which then is reflected in the NGINX ingress configuration.

By adding the custom annotation "custom.nginx.org/cors-allow-origin" to an ingress, with the value of the target server (i.e. "https://sample.server.org/"), the according NGINX ingress configuration is created in the "server {}" section:

# replace Access-Control-Allow-Origin header 
proxy_hide_header "Access-Control-Allow-Origin"; 
add_header Access-Control-Allow-Origin "https://sample.server.org";

Hiding the original header values proved to be required, as else the browser might complain about multiple set values.

Checklist

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

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

[codecov-commenter]

Codecov Report

Merging #3004 (cbbd5ff) into main (39eefc4) will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #3004      +/-   ##
==========================================
+ Coverage   52.54%   52.56%   +0.01%     
==========================================
  Files          58       58              
  Lines       16069    16069              
==========================================
+ Hits         8444     8446       +2     
+ Misses       7349     7347       -2     
  Partials      276      276              

Impacted Files	Coverage Δ
...ternal/k8s/appprotect/app_protect_configuration.go	86.74% <0.00%> (+0.57%)	⬆️

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[jasonwilliams14]

We are reviewing this internally and are planning this for a future release.