Add --publish-status-address to 2.x

[rainest]

What this PR does / why we need it:
This was originally added to #1451, but later removed. I thought that removal had been reverted, but it wasn't, and I got confused in the PR history and missed that before it went in.

Per #1305 we do want to include this in 2.x for 1.x flag parity. The flag is useful when IP information is missing from the publish service (e.g. bare metal clusters) or does not reflect the true external address of the proxy (e.g. when you chain proxies and have something else in front of Kong).

Lastly, this updates --publish-status-address to use a StringSlice, following the same logic as #1496. Note that 1.x --publish-status-address originally supported only a single IP, but we may as well allow multiple, as it's compatible.

Which issue this PR fixes:
fixes #1305 in conjunction with #1451

Special notes for your reviewer:

The reverted commit also included an additional new feature for deriving the Kong admin API URL from its Service, instead of providing it directly in --kong-admin-url. Per my comments in #1486 (which also includes the same feature) this isn't ready for merge yet, as it breaks some existing functionality (namely HTTPS). The admin API doesn't factor into status information at all, and it should be raised in a separate PR if we wish to include it.

Edit: this actually was already reverted... somewhere in history. It's in the reverted commit, but not in the diff here, so the above can be ignored for the context here.

This updates the changelog to reflect the 2.0.0-alpha.2 release. We forgot to do that for the actual release.

PR Readiness Checklist:

Complete these before marking the PR as ready to review:

• the CHANGELOG.md release notes have been updated to reflect any significant (and particularly user-facing) changes introduced by this PR

[github-actions]

Licenses differ between commit 3ef1829afcc6b6ba47a72d52f50559cfb976f9b7 and base:

+++ pr_licenses.csv	2021-07-07 19:26:42.204339053 +0000
@@ -1,3 +1,8 @@
+github.com/Masterminds/goutils,https://github.com/Masterminds/goutils/blob/master/LICENSE.txt,Apache-2.0
+github.com/Masterminds/semver,https://github.com/Masterminds/semver/blob/master/LICENSE.txt,MIT
+github.com/Masterminds/sprig,https://github.com/Masterminds/sprig/blob/master/LICENSE.txt,MIT
+github.com/alecthomas/template,https://github.com/alecthomas/template/blob/master/LICENSE,BSD-3-Clause
+github.com/alecthomas/units,https://github.com/alecthomas/units/blob/master/COPYING,MIT
 github.com/beorn7/perks/quantile,https://github.com/beorn7/perks/blob/master/quantile/LICENSE,MIT
 github.com/blang/semver/v4,https://github.com/blang/semver/blob/master/v4/LICENSE,MIT
 github.com/bombsimon/logrusr,https://github.com/bombsimon/logrusr/blob/master/LICENCE,MIT
@@ -7,6 +12,7 @@
 github.com/eapache/channels,https://github.com/eapache/channels/blob/master/LICENSE,MIT
 github.com/eapache/queue,https://github.com/eapache/queue/blob/master/LICENSE,MIT
 github.com/evanphx/json-patch,https://github.com/evanphx/json-patch/blob/master/LICENSE,BSD-3-Clause
+github.com/evanphx/json-patch/v5,https://github.com/evanphx/json-patch/blob/master/v5/LICENSE,BSD-3-Clause
 github.com/fatih/color,https://github.com/fatih/color/blob/master/LICENSE.md,MIT
 github.com/fsnotify/fsnotify,https://github.com/fsnotify/fsnotify/blob/master/LICENSE,BSD-3-Clause
 github.com/ghodss/yaml,https://github.com/ghodss/yaml/blob/master/LICENSE,MIT
@@ -25,16 +31,19 @@
 github.com/hashicorp/golang-lru,https://github.com/hashicorp/golang-lru/blob/master/LICENSE,MPL-2.0
 github.com/hashicorp/hcl,https://github.com/hashicorp/hcl/blob/master/LICENSE,MPL-2.0
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+github.com/huandu/xstrings,https://github.com/huandu/xstrings/blob/master/LICENSE,MIT
 github.com/imdario/mergo,https://github.com/imdario/mergo/blob/master/LICENSE,BSD-3-Clause
 github.com/json-iterator/go,https://github.com/json-iterator/go/blob/master/LICENSE,MIT
 github.com/magiconair/properties,https://github.com/magiconair/properties/blob/master/LICENSE.md,BSD-2-Clause
 github.com/mattn/go-colorable,https://github.com/mattn/go-colorable/blob/master/LICENSE,MIT
 github.com/mattn/go-isatty,https://github.com/mattn/go-isatty/blob/master/LICENSE,MIT
 github.com/matttproud/golang_protobuf_extensions/pbutil,https://github.com/matttproud/golang_protobuf_extensions/blob/master/pbutil/LICENSE,Apache-2.0
+github.com/mitchellh/copystructure,https://github.com/mitchellh/copystructure/blob/master/LICENSE,MIT
 github.com/mitchellh/mapstructure,https://github.com/mitchellh/mapstructure/blob/master/LICENSE,MIT
+github.com/mitchellh/reflectwalk,https://github.com/mitchellh/reflectwalk/blob/master/LICENSE,MIT
 github.com/modern-go/concurrent,https://github.com/modern-go/concurrent/blob/master/LICENSE,Apache-2.0
 github.com/modern-go/reflect2,https://github.com/modern-go/reflect2/blob/master/LICENSE,Apache-2.0
-github.com/pelletier/go-toml,https://github.com/pelletier/go-toml/blob/master/LICENSE,MIT
+github.com/pelletier/go-toml,https://github.com/pelletier/go-toml/blob/master/LICENSE,Apache-2.0
 github.com/pkg/errors,https://github.com/pkg/errors/blob/master/LICENSE,BSD-2-Clause
 github.com/prometheus/client_golang/prometheus,https://github.com/prometheus/client_golang/blob/master/prometheus/LICENSE,Apache-2.0
 github.com/prometheus/client_model/go,https://github.com/prometheus/client_model/blob/master/go/LICENSE,Apache-2.0
@@ -64,7 +73,7 @@
 go.uber.org/zap,Unknown,MIT
 gomodules.xyz/jsonpatch/v2,Unknown,Apache-2.0
 google.golang.org/protobuf,Unknown,BSD-3-Clause
-gopkg.in/evanphx/json-patch.v4,Unknown,BSD-3-Clause
+gopkg.in/alecthomas/kingpin.v2,Unknown,MIT
 gopkg.in/go-playground/pool.v3,Unknown,MIT
 gopkg.in/inf.v0,Unknown,BSD-3-Clause
 gopkg.in/ini.v1,Unknown,Apache-2.0
@@ -82,5 +91,5 @@
 knative.dev/networking/pkg,Unknown,Apache-2.0
 knative.dev/pkg,Unknown,Apache-2.0
 sigs.k8s.io/controller-runtime,Unknown,Apache-2.0
-sigs.k8s.io/structured-merge-diff/v4/value,Unknown,Apache-2.0
+sigs.k8s.io/structured-merge-diff/v4,Unknown,Apache-2.0
 sigs.k8s.io/yaml,Unknown,MIT```

[codecov]

Codecov Report

Merging #1509 (cb4f256) into next (ce45ce0) will decrease coverage by 0.16%.
The diff coverage is 70.00%.

@@            Coverage Diff             @@
##             next    #1509      +/-   ##
==========================================
- Coverage   51.52%   51.36%   -0.17%     
==========================================
  Files          91       91              
  Lines        6292     6300       +8     
==========================================
- Hits         3242     3236       -6     
- Misses       2757     2770      +13     
- Partials      293      294       +1     

Flag	Coverage Δ
integration-test	48.27% <70.00%> (-0.89%)	⬇️
unit-test	38.87% <30.00%> (+0.04%)	⬆️

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

Impacted Files	Coverage Δ
railgun/internal/ctrlutils/ingress-status.go	61.63% <50.00%> (-3.57%)	⬇️
railgun/manager/run.go	70.52% <100.00%> (ø)
railgun/pkg/config/config.go	92.94% <100.00%> (+0.25%)	⬆️
railgun/internal/diagnostics/server.go	57.57% <0.00%> (-21.22%)	⬇️
...n/internal/proxy/clientgo_cached_proxy_resolver.go	74.03% <0.00%> (-1.93%)	⬇️
...trollers/configuration/zz_generated_controllers.go	47.83% <0.00%> (ø)
pkg/parser/parser.go	84.51% <0.00%> (+1.25%)	⬆️
railgun/internal/ctrlutils/utils.go	86.27% <0.00%> (+3.92%)	⬆️

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[ccfishk]

Travis, thanks for taking care of this and clarifying that PublishStatusAddress can be read when a valid proxy public IP is not available . 💯

Questions:

1. can controller use PublishStatusAddress (the ip) communicate to kong proxy (whose ip is missed) for configuration update ? Or, is a separate route/ingress IP ?

2. which module (I don't think is Kong Admin API, is loaderbalancer/or other network resource) is associated to the PublishStatusAddress ? can we retrieve the address instead of hardcode parameter ?

thanks

[rainest]

can controller use PublishStatusAddress (the ip) communicate to kong proxy (whose ip is missed) for configuration update ? Or, is a separate route/ingress IP ?

No, it's the proxy IP, not the admin API IP. In either case, sending something through an external address when an internal path exists is usually not desired: it likely traverses a path with less bandwidth/more latency and may result in ingress/egress charges from a cloud provider.

which module (I don't think is Kong Admin API, is loaderbalancer/or other network resource) is associated to the PublishStatusAddress ? can we retrieve the address instead of hardcode parameter ?

It's an unknown network endpoint that the user promises will ultimately route to the proxy. This flag is intended specifically for cases where you cannot retrieve the address(es) from Kubernetes, e.g. an independent load balancer that points to the proxy's NodePort.