Asset data can now be copied in Python via assignment to
`id.asset_data`, so for example `dest.asset_data = source.asset_data`.
This copies the description, license, author, etc. fields, as well as
the tags and the asset catalog assignment.
This is intended to be used in the pose library, when updating a pose by
simply creating a new asset and having that replace the old one.
This is intentionally taking a copy, even though the above use case
could have sufficed with a higher-level 'move' function. By exposing
this as a copy, it can be used in a wider range of situations, from
whatever Python code wants to use it. This could include copying the
asset data from the active asset to all the other selected ones.
Any pre-existing asset data is freed before the copy is assigned. The
target ID MUST be marked as asset already for the assignment to work.
Assigning `None` to clear the asset status is not allowed. Instead
`.asset_mark()` resp. `.asset_clear()` should be used. This limitation
is in place to simplify the API, and to ensure that there is only one
way in which assets are marked/cleared, making it easier to change the
internals of the asset system without API changes.
Example code:
```python
src = bpy.data.objects['Suzanne']
dst = bpy.data.objects['Cube']
dst.asset_mark()
dst.asset_data = src.asset_data
```
Pull Request: https://projects.blender.org/blender/blender/pulls/108547