Support passing in Graph.artifacts

[JacobHayes]

Description

This makes Graph.artifacts a normal pydantic field, rather than a PrivateAttr with a @property getter. This means an existing set of Artifacts can be passed in directly (eg: when deserializing).

This also fixes a bug where the Graph.artifacts (and thus Producers / structure of the graph) wasn't actually encoded into the Graph.fingerprint. This wouldn't have broken builds since the snapshotting logic accounts for this in a similar way.

Pydantic has some caveats with copying dict subclasses that needed working around (and will likely need more when v2 is ready), but those are relatively minor.

---

I'll need to follow this up to ensure that the Graph.__enter__ logic (which populates arti.context.graph to allow resolving all of the path_tags in the Storages) is called, but that's a bit trickier until Pydantic supports post-init (where we have access to self) - I'll probably just override __init__ (but hopefully in a way that preserves the nice autogenerated hints and what not 🤞).

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Updated and expanded tests

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• 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 that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in upstream modules

[codecov]

Codecov Report

Merging #343 (78ba386) into golden (d708f3b) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            golden      #343   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           43        43           
  Lines         2790      2799    +9     
  Branches       706       710    +4     
=========================================
+ Hits          2790      2799    +9     

Impacted Files	Coverage Δ
src/arti/graphs/__init__.py	100.00% <100.00%> (ø)
src/arti/internal/models.py	100.00% <100.00%> (ø)

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more