add optional artifact

[mostaphaRoudsari]

This commit adds support for optional artifact inputs and outputs. This change will make it possible to support radiance recipes with BSDF materials.

@AntoineDao, I added an is_optional property to artifact input/outputs which can be used to update the extensions to support optional types.

[coveralls]

Pull Request Test Coverage Report for Build 506221767

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 25 of 35 (71.43%) changed or added relevant lines in 5 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.2%) to 49.585%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
queenbee/io/common.py	2	3	66.67%
queenbee/io/inputs/dag.py	8	9	88.89%
queenbee/io/outputs/alias.py	6	7	85.71%
queenbee/io/outputs/dag.py	6	7	85.71%
queenbee/io/inputs/alias.py	3	9	33.33%

Totals
Change from base Build 506217418:	0.2%
Covered Lines:	1373
Relevant Lines:	2769

---

💛 - Coveralls

[AntoineDao]

I'll merge this in just now so I can implement it on queenbee-argo ASAP.

[ladybugbot]

🎉 This PR is included in version 1.22.13 🎉

The release is available on:

• GitHub release
• v1.22.13

Your semantic-release bot 📦🚀