feat: allow overriding prev and next links in frontmatter (#15755) (#16044)

* feat: allow overriding prev and next links in frontmatter (#15755)

* build test successfully run locally

* implemented prev and next logic according to front matter

* added overriding prev and next in frontmatter

* cleaned code

* Update content/en/docs/ambient/install/_index.md

Co-authored-by: Craig Box <craig.box@gmail.com>

---------

Co-authored-by: Craig Box <craig.box@gmail.com>

content/en/docs/ambient/getting-started/_index.md

@@ -6,8 +6,9 @@ aliases:
   - /docs/ops/ambient/getting-started
   - /latest/docs/ops/ambient/getting-started
 owner: istio/wg-networking-maintainers
-skip_list: true
 test: yes
+skip_list: true
+next: /docs/ambient/getting-started/deploy-sample-app
 ---
 
 This guide lets you quickly evaluate Istio's {{< gloss "ambient" >}}ambient mode{{< /gloss >}}. You'll need a Kubernetes cluster to proceed. If you don't have a cluster, you can use [kind](/docs/setup/platform-setup/kind) or any other [supported Kubernetes platform](/docs/setup/platform-setup).

content/en/docs/ambient/getting-started/cleanup/index.md

@@ -4,6 +4,7 @@ description: Delete Istio and associated resources.
 weight: 6
 owner: istio/wg-networking-maintainers
 test: yes
+next: /docs/ambient/install
 ---
 
 If you no longer need Istio and associated resources, you can delete them by following the steps in this section.

content/en/docs/ambient/getting-started/deploy-sample-app/index.md

@@ -4,6 +4,7 @@ description: Deploy the Bookinfo sample application.
 weight: 2
 owner: istio/wg-networking-maintainers
 test: yes
+prev: /docs/ambient/getting-started
 ---
 
 To explore Istio, you will install the sample [Bookinfo application](/docs/examples/bookinfo/), composed of four separate microservices used to demonstrate various Istio features.

layouts/partials/posts_navigation.html

@@ -1,15 +1,25 @@
 {{ $skipPageNav := .Scratch.Get "skipPageNav" }}
 {{ if not (or .Params.skip_pagenav $skipPageNav) }}
-    {{ if or .NextInSection .PrevInSection }}
+    {{ $prev := .NextInSection }}
+    {{ $next := .PrevInSection }}
+    {{ with .Params.prev }}
+        {{$prev = $.Site.GetPage $.Site.Language.Lang .}}
+    {{ end }}
+
+    {{ with .Params.next }}
+        {{$next = $.Site.GetPage $.Site.Language.Lang .}}
+    {{ end }}
+
+    {{ if or $prev $next }}
         <nav class="pagenav">
             <div class="left">
-                {{ if .NextInSection }}
-                    <a title="{{ .NextInSection.Description }}" href="{{ .NextInSection.Permalink }}" class="next-link">{{- partial "icon.html" "left-arrow" -}}{{- .NextInSection.LinkTitle -}}</a>
+                {{ if $prev }}
+                    <a title="{{ $prev.Description }}" href="{{ $prev.Permalink }}" class="next-link">{{- partial "icon.html" "left-arrow" -}}{{- $prev.LinkTitle -}}</a>
                 {{ end }}
             </div>
             <div class="right">
-                {{ if .PrevInSection }}
-                    <a title="{{ .PrevInSection.Description }}" href="{{ .PrevInSection.Permalink }}" class="next-link">{{- .PrevInSection.LinkTitle -}}{{- partial "icon.html" "right-arrow" -}}</a>
+                {{ if $next }}
+                    <a title="{{ $next.Description }}" href="{{ $next.Permalink }}" class="next-link">{{- $next.LinkTitle -}}{{- partial "icon.html" "right-arrow" -}}</a>
                 {{ end }}
             </div>
         </nav>