Configure uncacheable delivery services in Varnish

[AbdelrahmanElawady]

Skip caching delivery services with type HTTP_NO_CACHE.

Closes: #7770

---

Which Traffic Control components are affected by this PR?

• Traffic Control Cache Config (t3c, formerly ORT)

What is the best way to verify this PR?

unit tests added.
CIAB doesn't have a DS with no cache type, however if manually changed the DS profile to HTTP_NO_CACHE requests should not be cached with Varnish.

PR submission checklist

• This PR has tests
• This PR has documentation
• This PR has a CHANGELOG.md entry
• This PR DOES NOT FIX A SERIOUS SECURITY VULNERABILITY (see the Apache Software Foundation's security guidelines for details)

[codecov]

Codecov Report

Merging #7771 (63fca4f) into master (75ec56f) will decrease coverage by 36.24%.
Report is 132 commits behind head on master.
The diff coverage is 40.57%.

@@              Coverage Diff              @@
##             master    #7771       +/-   ##
=============================================
- Coverage     65.05%   28.82%   -36.24%     
  Complexity       98       98               
=============================================
  Files           314      599      +285     
  Lines         12365    77053    +64688     
  Branches        907       90      -817     
=============================================
+ Hits           8044    22210    +14166     
- Misses         3968    52753    +48785     
- Partials        353     2090     +1737     

Flag	Coverage Δ
golib_unit	53.66% <54.88%> (?)
grove_unit	12.02% <ø> (?)
t3c_unit	5.96% <2.74%> (?)
traffic_monitor_unit	26.44% <ø> (?)
traffic_ops_unit	21.45% <ø> (?)
traffic_portal_v2	?
traffic_stats_unit	10.78% <ø> (?)
unit_tests	25.63% <40.57%> (-48.15%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
cache-config/t3c-apply/config/config.go	0.00% <0.00%> (ø)
cache-config/t3c-apply/torequest/cmd.go	0.00% <0.00%> (ø)
cache-config/t3c-check-refs/t3c-check-refs.go	1.78% <0.00%> (ø)
cache-config/t3c-generate/cfgfile/varnish.go	0.00% <0.00%> (ø)
cache-config/t3c-generate/config/config.go	0.81% <0.00%> (-0.08%)	⬇️
cache-config/t3c-generate/t3c-generate.go	0.00% <ø> (ø)
lib/go-atscfg/parentabstraction.go	80.00% <ø> (ø)
lib/go-tc/cdns.go	0.00% <ø> (ø)
lib/go-tc/deliveryservice_servers.go	0.00% <0.00%> (ø)
lib/go-tc/federation_resolver.go	45.45% <0.00%> (ø)
... and 13 more

... and 484 files with indirect coverage changes

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[limited]

Here's the generated VCL from this change:

sub vcl_recv {
	if ((req.method == "PUSH" || req.method == "PURGE" || req.method == "DELETE") && !client.ip ~ allow_all) {
		return (synth(405));
	}
	if (req.method == "PURGE") {
		return (purge);
	}
	if (req.http.host == "edge.demo1.mycdn.ciab.test") {
		set req.backend_hint = demo1.backend();
	}
	if (req.http.host == "video.demo2.mycdn.ciab.test") {
		set req.backend_hint = demo2.backend();
	}
}
sub vcl_backend_response {
	if (bereq.http.host == "origin.infra.ciab.test") {
		set beresp.uncacheable = true;
	}
}
sub vcl_backend_fetch {
	if (bereq.http.host == "edge.demo1.mycdn.ciab.test") {
		set bereq.http.host = "origin.infra.ciab.test";
	}
	if (bereq.http.host == "video.demo2.mycdn.ciab.test") {
		set bereq.http.host = "origin.infra.ciab.test";
	}
}

Because the same origin is shared between both delivery services, this will mark all requests to origin.infra.ciab.test as uncacheable.

Is there a way we can restrict the DS_NO_CACHE behavior just to the appropriate delivery service? (Maybe based on bereq.http.Host?)

[limited]

Because the same origin is shared between both delivery services, this will mark all requests to origin.infra.ciab.test as uncacheable.

After comparing with the existing ATS implementation, this matches current behavior, so keeping it for consistency.