Add Device Agent on Kubernetes documentation

[hardillb]

closes #6578

Description

Describes 2 deployment options

• pre-configured device.yml
• provisioning token

This is bare minimum docs, might need some more "why" language at the top...

Related Issue(s)

#6578

Checklist

• I have read the contribution guidelines
• Suitable unit/system level tests have been added and they pass
• Documentation has been updated
  • Upgrade instructions
  • Configuration details
  • Concepts
• Changes flowforge.yml?
  • Issue/PR raised on FlowFuse/helm to update ConfigMap Template
  • Issue/PR raised on FlowFuse/CloudProject to update values for Staging/Production
• Link to Changelog Entry PR, or note why one is not needed.

Labels

• Includes a DB migration? -> add the area:migration label

[ppawlowski]

I thought about placing manifests in the device agent repo, in the examples directory, to make it easier to reference in some kind of scripts/pipelines/etc. It will also be easier for us to automatically scan them and keep image tags up to date. WDYT?

[hardillb]

I might just change them to :latest 😛

But yeah, they should probably end up in there as well

[ppawlowski]

@hardillb please check my changes. Merge the PR anytime.

[ppawlowski]

To clarify: the navOrder value change in the README.md file fixes ordering in the higher level navigation in the sidebar.

Current:

After the order change:

[allthedoll]

I am still reviewing 😇

[allthedoll]

Since this deployment uses a single pvc and provisioning token, should we explicitly note that this example assumes one device agent per deployment and should not be scaled beyond one replica?

[hardillb]

We could add a note that horizontal scaling requires using a StatefulSet

[allthedoll]

since this initContainer only copies the file if it does not already exist, should we add a short note explaining that the provisioning configuration is only applied on first start and that subsequent restarts preserve the existing device.yml on the pvc?

[allthedoll]

this assumes the cluster has a default StorageClass. Should we add a brief note that users may need to set storageClassName depending on their Kubernetes setup, for example storageClassName: <your-storage-class>?

Also, should we mention what gets stored here (the updated device.yml and installed nodes) so users can size the pvc appropriately?

[allthedoll]

I added a gpt suggested why/when if you care for it @hardillb. Otherwise it's looking good.