feat(emby): Enable autodiscovery (#30924)

**Description**
<!--
Adds autodiscovery to Emby. When enabled, this change adds a DaemonSet
that will listen to broadcast udp packets on port 7359 and forward them
to the main emby pod. This allows Emby apps to easily find the server
when on the same local network.
-->
⚒️ 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?**
<!--
I tested this change on my cluster. I confirmed my android Emby app was
able to find my server after resetting the app.
My cluster helm-release.yaml can be found here:
https://github.com/Brocklobsta/cluster/blob/main/clusters/main/kubernetes/apps/emby/app/helm-release.yaml
-->

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

**✔️ Checklist:**

- [ ] ⚖️ My code follows the style guidelines of this project
- [x] 👀 I have performed a self-review of my own code
- [x] #️⃣ 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
- [x] I made sure the title starts with `feat(chart-name):`,
`fix(chart-name):` or `chore(chart-name):`

**➕ 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`

---

_Please don't blindly check all the boxes. Read them and only check
those that apply.
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---------

Signed-off-by: Brocklobsta <brock.d.allen@gmail.com>
Signed-off-by: Alfred Göppel <43101280+alfi0812@users.noreply.github.com>
Co-authored-by: Alfred Göppel <43101280+alfi0812@users.noreply.github.com>

charts/stable/emby/Chart.yaml

@@ -33,5 +33,6 @@ sources:
   - https://ghcr.io/elfhosted/emby
   - https://github.com/linuxserver/docker-emby.git
   - https://github.com/truecharts/charts/tree/master/charts/stable/emby
+  - https://hub.docker.com/r/alpine/socat
 type: application
-version: 22.2.2
+version: 22.4.0

charts/stable/emby/values.yaml

@@ -2,6 +2,10 @@ image:
   repository: ghcr.io/elfhosted/emby
   pullPolicy: IfNotPresent
   tag: 4.9.0.37@sha256:f2993275af1b96127cfcb10f2e87403cd35645263730785cd5f372c0f768aa38
+broadcastProxyImage:
+  repository: docker.io/alpine/socat
+  pullPolicy: IfNotPresent
+  tag: 1.8.0.0@sha256:a6be4c0262b339c53ddad723cdd178a1a13271e1137c65e27f90a08c16de02b8
 securityContext:
   container:
     readOnlyRootFilesystem: false
@@ -11,6 +15,14 @@ service:
       main:
         port: 10079
         targetPort: 8096
+  autodiscovery:
+    enabled: "{{ .Values.autodiscovery.enabled }}"
+    ports:
+      autodiscovery:
+        enabled: true
+        protocol: udp
+        port: 7359
+        targetPort: 7359
 workload:
   main:
     podSpec:
@@ -27,6 +39,56 @@ workload:
               type: http
               path: /
           env: {}
+  broadcastproxy:
+    enabled: "{{ .Values.autodiscovery.enabled }}"
+    type: Deployment
+    podSpec:
+      hostNetwork: true
+      # Proxy doesn't seem to respect the TERM signal, so by default
+      # this ends up just hanging until the default grace period ends.
+      # This is unnecesary since this workload only proxies autodiscovery
+      # messages.
+      terminationGracePeriodSeconds: 3
+      containers:
+        broadcastproxy:
+          enabled: true
+          primary: true
+          imageSelector: broadcastProxyImage
+          securityContext:
+            readOnlyRootFilesystem: true
+          command: ["/bin/sh"]
+          # Quite a lot going on here:
+          # - Resolve Emby's autodiscovery service IP from its FQDN via getent hosts
+          # - Export the IP to `$TARGET_IP`
+          # - Check `$TARGET_IP` is not empty (so we can crash if it is - will help to detect templating errors)
+          # - Touch `/tmp/healty` to use with the readiness, liveness and startup probes
+          # - Start socat in proxy mode
+          # - On exit remove `/tmp/healthy`
+          args:
+            - "-c"
+            - 'export TARGET_IP=$(getent hosts ''{{ printf "%v-autodiscovery" (include "tc.v1.common.lib.chart.names.fullname" $) }}'' | awk ''{ print $1 }'') && [[ ! -z $TARGET_IP ]] && touch /tmp/healthy && socat -T1 UDP4-LISTEN:7359,fork,reuseaddr,rcvbuf=8096 UDP4-SENDTO:$TARGET_IP:7359,rcvbuf=8096 ; rm -rf /tmp/healthy'
+          probes:
+            readiness:
+              enabled: true
+              type: exec
+              command:
+                - cat
+                - /tmp/healthy
+            liveness:
+              enabled: true
+              type: exec
+              command:
+                - cat
+                - /tmp/healthy
+            startup:
+              enabled: true
+              type: exec
+              command:
+                - cat
+                - /tmp/healthy
+# -- enable Emby autodiscovery on LAN
+autodiscovery:
+  enabled: false
 persistence:
   config:
     enabled: true