Add ability to view all post types when Pulling from an External Connection

[dkotter]

Is your enhancement related to a problem? Please describe.

When you go to the Pull screen for an Internal/Network Connection, we default to showing content from all supported post types. You can then filter down to just the post type you want (like Posts).

But for External Connections, we default to showing just Posts and there isn't a way to view content across all post types. This is because historically we were requesting content from a post type specific endpoint, so it was impossible to get content across multiple post types. But with the changes introduced in #811, we can now show content from across all supported post types, mirroring how we do this for Internal Connections.

One thing to note here is if you are on an External Connection that has had no content pulled or skipped yet, we utilize the old approach to grabbing content, from a post type specific endpoint and not the new endpoint introduced in #811. So that will need to be addressed here to fully support his new feature.

Code of Conduct

• [X] I agree to follow this project's Code of Conduct

[jeffpaul]

Noting that https://github.com/10up/distributor/tree/feature/861 may be a good start on this, so we'll want to credit @chigozieorunta once this issue gets resolved.

[peterwilsoncc]

As work in beginning on Distributor 2.0.0, I've moved this enhancement off the 1.7.0 milestone to allow the point release to focus on bug fixes.

[mehul0810]

@jeffpaul I have worked on this with the branch https://github.com/10up/distributor/tree/feature/861, tested the functionality and created a PR which is ready for review.

[ankitrox]

@mehul0810 This PR is also there, please check if there's something you can spot or helpful.

[peterwilsoncc]

I've moved this to 2.0.1 as the REST API endpoint this relies on will be getting modified in 2.0.0.