Make remote preview works for drafts on self hosted sites

[maxme]

Make remote preview works for drafts on self hosted sites

Fist discussed here: #10212 (comment)

To test:

Case 1:

• On a self hosted site (not connected via Jetpack)
• Open a published post and modify its content
• Tap the "Preview" button in the overflow menu
• You should get a "Preview unavailable" screen

Case 2:

• On a self hosted site (not connected via Jetpack)
• Create (or edit) a draft
• Tap the "Preview" button in the overflow menu
• You should get a the preview screen (after a "Saving" progress popover).

Update release notes:

• If there are user facing changes, I have added an item to RELEASE-NOTES.txt.

[peril-wordpress-mobile]

	Warnings
⚠️	PR is not assigned to a milestone.

Generated by 🚫 dangerJS

[shiki]

@maxme This is looking good. I have one suggestion (⭐️) for your consideration. If you don't agree, feel free to merge.

I'd also like to note that it's possible for a user to turn a published post into a draft when using Preview. Steps:

1. Edit a published post
2. Go to Post Settings and change the Status to Draft.
3. Exit Post Settings and click on Preview.

The post will be uploaded and changed to a draft. I don't think we should fix this right away. I believe we've had a discussion about this UI in one of the Offline Posting tickets. I can't quite remember what our decision for that was.

Luckily, it's not possible to accidentally publish something. 🤷‍♂

[maxme]

I'd also like to note that it's possible for a user to turn a published post into a draft when using Preview. Steps:

1. Edit a published post
2. Go to Post Settings and change the Status to Draft.
3. Exit Post Settings and click on Preview.

Yes, it's possible to unpublish that way, but that sounds more like a problem with the Post Settings status than related to this change. Also note this is possible on any kind of site (Self hosted, Jetpack or wpcom).

Ready for a second pass.

[shiki]

Thank you, @maxme!

but that sounds more like a problem with the Post Settings status than related to this change.

I agree.