New filter: allow content classification by $post_status

[jamesmorrison]

Is your enhancement related to a problem? Please describe.
Currently, there is no hook / filter to enable content classification based on $post_status; content classification can only be processed where a post is actually published.

// Only process published, supported items and only if features are enabled
if ( 'publish' === $post_status && in_array( $post_type, $supported, true ) && \Classifai\language_processing_features_enabled() ) {
	$this->classify( $post_id );
}

https://github.com/10up/classifai/blob/develop/includes/Classifai/Admin/SavePostHandler.php#L66

Describe the solution you'd like
An additional filter; which allows an array of post statuses to be used. This will allow (for example) a post with post status draft to be processed (prior to publication).

Designs
N/A - functional changes only

Describe alternatives you've considered
Externally, the Classifai\Admin\SavePostHandler class could be extended to allow the same change.

[jeffpaul]

Tagging in @dkotter to confirm best approach on this before we get someone to work on this / align to a milestoned release.

[dkotter]

Left comments on the PR but to capture those here as well, I think we can copy how we do the supported post types, by adding a new helper method to get the supported post stati with a filter there. We could also add these as options to our settings page, which might be nice.

[jeffpaul]

@jamesmorrison @dkotter did these options get added to the settings page or should we open a subsequent issue to track that work?

[dkotter]

Yes, these got added to the settings screen