Assets keep their own stac_extensions

[constantinius]

Related Issue(s):

• Allow extensions for un-parented assets #793

Description:

This PR aims to make Asset objects more independent, i.e allow to extend them, even if they are not yet inserted into an Item/Collection.

This is achieved by letting assets keep their own stac_extensions list, which is merged with the Items/Collections stac_extension in the respective to_dict function

Other relevant changes:

• Deprecating validate_owner_has_extension
• Switching from validate_owner_has_extension to ensure_has_extension in extensions dealing with assets

PR Checklist:

• pre-commit hooks pass locally
• Tests pass (run scripts/test)
• Documentation has been updated to reflect changes, if applicable
• This PR maintains or improves overall codebase code coverage.
• Changes are added to the CHANGELOG. See the docs for information about adding to the changelog.

[gadomski]

The idea seems reasonable to me, though my inclination is to make the attribute private on an asset, e.g.:

class Asset:
    _stac_extensions: List[str]
    ...

It's not part of the spec, it's a PySTAC implementation detail, so users shouldn't be touching it themselves.

[constantinius]

765a05f does that.

This makes the extension handling more complex now, though, as we have to introduce a couple of new code paths as we cannot simply treat assets as objects having a stac_extensions: Optional[List[str]].

What would you say?

[gadomski]

This makes the extension handling more complex now, though, as we have to introduce a couple of new code paths as we cannot simply treat assets as objects having a stac_extensions: Optional[List[str]].

You're right, that is pretty awkward. Maybe _stac_extensions was a bad idea 😬. Let's remove 765a05f for now and keep it at stac_extensions. Thanks for trying that out 🙇🏼.