docs: add comprehensive base job template examples for Kubernetes

[kingsley-123]

Summary

This PR adds a new section with comprehensive examples for customizing the Kubernetes base job template, addressing common configuration patterns that users frequently need.

Related to the Helm chart documentation improvements in PrefectHQ/prefect-helm#566.

Changes

• Added "Base Job Template Examples" section to the Kubernetes deployment guide
• Included detailed examples for:
  • Environment variables configuration
  • Secret references for sensitive data
  • Image pull secrets for private registries
  • Resource limits and requests (CPU and memory)
• Added explanation of the two-part template structure (variables + job_configuration)
• Included warning about variable reference requirements

Motivation

While working on Helm chart documentation, I identified that users needed more concrete examples of base job template customization. The existing documentation mentioned the advanced tab but didn't provide comprehensive patterns for common use cases.

These examples are based on production Kubernetes deployment patterns and will help users configure their work pools more effectively.

Testing

Validated JSON syntax for all examples.

[desertaxle]

Thanks for the fantastic examples, @kingsley-123!

Since this guide is already pretty long, could you split these out into their own page under Advanced > Workflow Infrastructure? Something like "Customizing Base Job Templates." They're great and deserve to be easy to find.

[kingsley-123]

@desertaxle

Thanks for the feedback! That makes sense a dedicated page will make these examples easier to find.

I'll create a new page under Advanced > Workflow Infrastructure as you suggested. Should I title it "Customizing Base Job Templates" or would you prefer something more specific like "Customizing Kubernetes Base Job Templates"?

I'll have the update ready soon.

[kingsley-123]

@desertaxle
I've moved the examples to a dedicated page at docs/v3/advanced/customize-base-job-templates.mdx as you suggested.

The Kubernetes guide now includes a link to this new page, making the examples easier to find while keeping the main guide focused.

Ready for another review. Thanks for the feedback!

[desertaxle]

@kingsley-123 you'll need to add an entry to this list in docs/docs.json to make sure this new page shows up in the docs.

[kingsley-123]

@desertaxle, I've added the entry to docs/docs.json under the Extensibility section. The page should now appear in the navigation menu.

[desertaxle]

LGTM! Thanks @kingsley-123!