feat(clusterissuer): Add cluster certificate docs and replace experimental label with advanced (#14372)

**Description**
<!--
Please include a summary of the change and which issue is fixed. Please
also include relevant motivation and context. List any dependencies that
are required for this change.
-->
⚒️ Fixes  # <!--(issue)-->

**⚙️ 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?**
<!--
Please describe the tests that you ran to verify your changes. Provide
instructions so we can reproduce. Please also list any relevant details
for your test configuration
-->

**📃 Notes:**
<!-- Please enter any other relevant information here -->

**✔️ Checklist:**

- [X] ⚖️ My code follows the style guidelines of this project
- [X] 👀 I have performed a self-review of my own code
- [ ] #️⃣ I have commented my code, particularly in hard-to-understand
areas
- [X] 📄 I have made corresponding changes to the documentation
- [X] ⚠️ My changes generate no new warnings
- [ ] 🧪 I have added tests to this description that prove my fix is
effective or that my feature works
- [X] ⬆️ 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 opened a PR on
[truecharts/containers](https://github.com/truecharts/containers) adding
the container to TrueCharts mirror repo.
- [ ] 🖼️ I have added an icon in the Chart's root directory called
`icon.png`

---

_Please don't blindly check all the boxes. Read them and only check
those that apply.
Those checkboxes are there for the reviewer to see what is this all
about and
the status of this PR with a quick glance._

charts/enterprise/clusterissuer/Chart.yaml

@@ -21,7 +21,7 @@ sources:
   - https://github.com/truecharts/charts/tree/master/charts/enterprise/clusterissuer
   - https://cert-manager.io/
 type: application
-version: 4.2.5
+version: 4.2.6
 annotations:
   truecharts.org/category: core
   truecharts.org/SCALE-support: "true"

charts/enterprise/clusterissuer/docs/cluster-certificates.md

@@ -0,0 +1,42 @@
+# Cluster Certificates Setup Guide
+
+This guide will walk you through setting up and using `cluster certificates`.
+
+:::note
+
+Since this is an advanced feature, it is not covered by Truecharts support.
+
+:::
+
+## Prerequisites
+
+- Ensure you have completed the [clusterissuer Setup Guide](how-to)
+- Install the `kubernetes-reflector` app from the `enterprise` train
+
+## Creating a cluster certificate
+
+In the clusterissuer app settings create a new "Cluster-Wide certificate". As with a [single domain certificate](how-to#configure-ingress-using-clusterissuer), input a cert-manager issuer (for example an ACME issuer you configured previously), a list of hosts for which the certificate is valid (you can use wildcards), and a name you will use to reference it.
+
+:::note
+
+In order for an ACME issuer to issue a wildcard certificate, you need to have a DNS01 challenge solver configured.
+
+:::
+
+![clusterissuer6](img/clusterissuer6.png)
+
+After creating the cluster certificate, verify it is working by checking the `Application Events` created in the `clusterissuer` app (see [how to verify a single app certificate is working](how-to#verifying-clusterissuer-is-working) for more information).
+
+## Using a cluster certificate
+
+After you have verified the certificate was created successfully, edit the settings of the app you wish to use it for and go to the _Ingress_ section.
+
+If you have previously used a single domain certificate from clusterissuer, remove the specified issuer name. Then, click on _Show Advanced Settings_  and add a _TLS_ entry. Enter the name of your cluster certificate, and the certificate host(s) which it will be used for. These are usually the same as your app host(s), unless you wish to use more than one certificate. Save the chart.
+
+:::note
+
+In order for your cluster certificate to show up as valid, the certificate hosts it is used for must match the ones specified when creating it in the clusterissuer app settings. For example, in this case we configure the certificate host `jellyfin.example.com`, which matches the configured wildcard certificate host (`*.example.com`).
+
+:::
+
+![clusterissuer7](img/clusterissuer7.png)

charts/enterprise/clusterissuer/questions.yaml

@@ -331,7 +331,7 @@ questions:
 
   - variable: clusterCertificates
     group: App Configuration
-    label: Cluster Wide Certificates (Experimental)
+    label: Cluster Wide Certificates (Advanced)
     description: "Creates certificates for use within the entire cluster. Can be used to create wildcard certificates."
     schema:
       additional_attrs: true