Added support for custom adapter hooks

[timlehr]

Summarize your change.

Rebased PR #1711

Required by OpenTimelineIO/otio-aaf-adapter#43

This adds support for attributing custom hooks to adapters and executing them with hook_function_argument_map being passed along through the adapter IO functions.

Describe the reason for the change.

I added two custom hooks to the OTIO AAF adapter (OpenTimelineIO/otio-aaf-adapter#43), allowing for embedding of media essence into the resulting AAF. This was needed to facilitate just-in-time DNXHR transcoding of the media for the AAF creation and adding a certain level of control and flexibility to the feature.

These features to the core are required in order to properly pass the hook argument map along to potential custom hooks run by the adapter. I tried to work with _FEATURE_MAP instead of creating a new version of the Adapter schema in order to minimize the impact of this change, while adding the necessary changes to facilitate custom hooks for adapters.

Reference associated tests.

tests/test_adapter_plugin.py
tests/test_hooks_plugins.py

[timlehr]

@ssteinbach I finally had some time to revive #1711. Please have a look when you find some time. Thank you! 🙏

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 90.69767% with 4 lines in your changes missing coverage. Please review.

Project coverage is 84.81%. Comparing base (c0e97b0) to head (87f0c74).
Report is 41 commits behind head on main.

Files with missing lines	Patch %	Lines
...-opentimelineio/opentimelineio/adapters/adapter.py	73.33%	2 Missing and 2 partials ⚠️

❌ Your changes status has failed because you have indirect coverage changes. Learn more about Unexpected Coverage Changes and reasons for indirect coverage changes.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1801      +/-   ##
==========================================
+ Coverage   84.11%   84.81%   +0.69%     
==========================================
  Files         198      177      -21     
  Lines       22241    12779    -9462     
  Branches     4687     1186    -3501     
==========================================
- Hits        18709    10839    -7870     
+ Misses       2610     1760     -850     
+ Partials      922      180     -742     

Flag	Coverage Δ
py-unittests	84.81% <90.69%> (+0.69%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...sts/baselines/custom_adapter_hookscript_example.py	100.00% <100.00%> (ø)
tests/baselines/example.py	100.00% <100.00%> (ø)
tests/test_adapter_plugin.py	91.27% <100.00%> (+3.43%)	⬆️
tests/test_hooks_plugins.py	98.01% <100.00%> (+0.29%)	⬆️
...-opentimelineio/opentimelineio/adapters/adapter.py	78.18% <73.33%> (-10.82%)	⬇️

... and 126 files with indirect coverage changes

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[timlehr]

@ssteinbach @jminor Finally rebased this again 👍

[ssteinbach]

The code looks good. This could use a note in the hook scripts documentation:

https://opentimelineio.readthedocs.io/en/latest/tutorials/write-a-hookscript.html

and adding it to the pluginfo script as well would be nice. I think all you need to do is add a "hooks" field to the plugin feature map:

OpenTimelineIO/src/py-opentimelineio/opentimelineio/plugins/python_plugin.py

Line 77 in 9deff1d

def plugin_info_map(self):