WPContextualOption

[oguzkocer]

As we discussed on Slack, it seems /users endpoint doesn't always return the avatar_urls field as promised in the documentation.

Unfortunately, I haven't foreseen the possibility of adding Option<T> to our generated contextual types such as UserWithEditContext when I worked on wp_contextual. This PR adds a new field attribute WPContextualOption which will leave the type of the field as is - without any modification. Just as a reminder, with WPContext and WPContextualField attributes, the type was always modified. (by removing the Option wrapper & Sparse prefix respectively)

This new attribute should be used alongside WPContext as without it, the field wouldn't be included in the contextual type in the first place. It also can not be used with WPContextualField because while WPContextualField will remove the Sparse prefix from the type, WPContextualOption will leave it as-is. So, they are incompatible.

All these cases are handled with proper errors, and integration tested. The documentation is also updated.

Before reviewing the implementation, I suggest taking a look at the new integration tests and the documentation to better understand the changes.

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To Test

• make test-server && make dump-mysql && make backup-wp-content-plugins
• cargo test --test '*' -- --nocapture --test-threads 1

[oguzkocer]

@jkmassel @crazytonyli I'll update the PR with the base branch once it's reviewed and approved. There is a lot of traffic in trunk at the moment, so it'll likely go out of date soon anyway.

[jkmassel]

I only understand about 80% of this, but the tests are very understandable (as is the new branch for is_wp_contextual_option_ident so I'm confident this will be solid.

Feel free to merge when convenient for you