Mark max_decommission_year as optional

[tsmbland]

Description

Marking this parameter as optional, and describing the default. It would be nice to automatically mark optional parameters, but that's probably more effort than it's worth

Copilot also flagged that we reject max_decommission_year = commission_year, which wasn't correct in the docs before, so I've updated this and added a test.

Fixes #1219

Type of change

• Bug fix (non-breaking change to fix an issue)
• New feature (non-breaking change to add functionality)
• Refactoring (non-breaking, non-functional change to improve maintainability)
• Optimization (non-breaking change to speed up the code)
• Breaking change (whatever its nature)
• Documentation (improve or add documentation)

Key checklist

• All tests pass: $ cargo test
• The documentation builds and looks OK: $ cargo doc
• Update release notes for the latest release if this PR adds a new feature or fixes a bug
  present in the previous release

Further checks

• Code is commented, particularly in hard-to-understand areas
• Tests added that prove fix is effective or that feature works

[Copilot]

Pull request overview

This PR updates the asset input schema documentation to explicitly mark max_decommission_year as optional and to describe its default behaviour, addressing issue #1219.

Changes:

• Update max_decommission_year field notes to state it is optional.
• Document the default when max_decommission_year is omitted.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.80%. Comparing base (934b359) to head (687b87b).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1354   +/-   ##
=======================================
  Coverage   88.80%   88.80%           
=======================================
  Files          58       58           
  Lines        8516     8516           
  Branches     8516     8516           
=======================================
  Hits         7563     7563           
  Misses        640      640           
  Partials      313      313           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.