feat(common): prevent the use of ix- namespace prefix outside of SCALE-Apps (#752)

**Description**
Some users are fucking around trying to get kubeapps recognised by
SCALE, this is PRECISELY what iX-Systems **and** TrueCharts do **NOT**
want. As fucking around with this, **will** lead to inherent issues.
Only to have people play dumb and file support tickets at either party

**⚙️ Type of change**

- [x] ⚙️ Feature/App addition
- [ ] 🪛 Bugfix
- [ ] ⚠️ Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] 🔃 Refactor of current code

**🧪 How Has This Been Tested?**
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**📃 Notes:**
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**✔️ Checklist:**

- [ ] ⚖️ My code follows the style guidelines of this project
- [ ] 👀 I have performed a self-review of my own code
- [ ] #️⃣ I have commented my code, particularly in hard-to-understand
areas
- [ ] 📄 I have made corresponding changes to the documentation
- [ ] ⚠️ My changes generate no new warnings
- [ ] 🧪 I have added tests to this description that prove my fix is
effective or that my feature works
- [ ] ⬆️ I increased versions for any altered app according to semantic
versioning

**➕ App addition**

If this PR is an app addition please make sure you have done the
following.

- [ ] 🖼️ I have added an icon in the Chart's root directory called
`icon.png`

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library/common/Chart.yaml

@@ -15,7 +15,7 @@ maintainers:
 name: common
 sources: null
 type: library
-version: 20.1.1
+version: 20.1.2
 annotations:
   artifacthub.io/category: "integration-delivery"
   artifacthub.io/license: "BUSL-1.1"

library/common/templates/lib/metadata/_namespace.tpl

@@ -28,6 +28,9 @@
         {{- fail (printf "%s - Namespace [%v] expected to have [ix-] prefix when installed in TrueNAS SCALE" $caller $namespace) -}}
       {{- end -}}
     {{- end -}}
+  {{- else if and (hasPrefix "ix-" $namespace) ( not $rootCtx.Values.global.ixChartContext ) -}}
+      {{/* Users should not use SCALE-reserved Namespace prefixes to hack things into the SCALE GUI */}}
+        {{- fail (printf "%s - Namespace [%v] is not allowed to have [ix-] prefix when installed outside of SCALE-Apps" $caller $namespace) -}}
   {{- end -}}
 
   {{- $namespace -}}