Implement Exact HTTPHeaderMatch

[nak3]

This patch adds Exact HTTPHeaderMatch support.

Fixes #3356

Signed-off-by: Kenjiro Nakayama nakayamakenjiro@gmail.com

/cc @stevesloka @youngnick @sunjayBhatia

[codecov]

Codecov Report

Merging #3538 (170db70) into main (298d3d2) will increase coverage by 0.03%.
The diff coverage is 100.00%.

❗ Current head 170db70 differs from pull request most recent head 4b6e734. Consider uploading reports for the commit 4b6e734 to get more accurate results

@@            Coverage Diff             @@
##             main    #3538      +/-   ##
==========================================
+ Coverage   76.23%   76.27%   +0.03%     
==========================================
  Files         100      100              
  Lines        6892     6903      +11     
==========================================
+ Hits         5254     5265      +11     
  Misses       1521     1521              
  Partials      117      117              

Impacted Files	Coverage Δ
internal/status/httproutestatus.go	34.54% <ø> (ø)
internal/dag/gatewayapi_processor.go	84.55% <100.00%> (+1.51%)	⬆️

[sunjayBhatia]

probably need a nil check on the Path field as well, since it can be omitted

probably should add a test that adds a header match but no path match (which should result in a default / prefix match) to ensure this is covered

[nak3]

Added match.Path.Value == "" || match.Path.Type == "" check since match.Path was changed to pointer recently by kubernetes-sigs/gateway-api@9d63656 (not included in current gateway-api release) so we need to change it to nilt check when gateway-api lib is updated.