Publish Button: Submit for review as pending for contributor

[aduth]

Closes #2029
Closes #2547

This pull request seeks to account for user capability in deciding the behavior of the Publish button. Specifically, if a user is not capable of publishing posts, they must Submit for Review instead, flagging the post as Pending.

Testing instructions:

1. Navigate to the post editor
2. Note that...
   • If your current user has ability to publish posts, the Publish button shows as Publish
   • Otherwise, the Publish button shows as Submit for Review

The "Submit for Review" label should take priority over all other scenarios, including updating an existing post and setting a post into the future.

[codecov]

Codecov Report

Merging #2526 into master will increase coverage by 0.44%.
The diff coverage is 92.3%.

@@            Coverage Diff             @@
##           master    #2526      +/-   ##
==========================================
+ Coverage    30.2%   30.65%   +0.44%     
==========================================
  Files         174      174              
  Lines        5270     5268       -2     
  Branches      900      902       +2     
==========================================
+ Hits         1592     1615      +23     
+ Misses       3121     3102      -19     
+ Partials      557      551       -6

Impacted Files	Coverage Δ
editor/header/tools/publish-button.js	88.46% <92.3%> (+88.46%)	⬆️

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[youknowriad]

Thanks a lot for these tests, these are very useful.

[youknowriad]

The context edit is awesome :). Seems like a hidden feature

[youknowriad]

Works great for me!

I don't know if we want a special notice for this, or if the "saved" status is enough.

[aduth]

I don't know if we want a special notice for this, or if the "saved" status is enough.

Yeah, we should probably want some messaging. The current editor shows a "Post submitted" after submitting for review. We can do similarly in the effects for publishing a post, but we'll want to think through ramifications of considering "pending" as a published state.

gutenberg/editor/effects.js

Lines 91 to 97 in 5f0fe6f

	const publishStatus = [ 'publish', 'private', 'future' ];
	const isPublished = publishStatus.indexOf( previousPost.status ) !== -1;
	const messages = {
	publish: __( 'Post published!' ),
	private: __( 'Post published privately!' ),
	future: __( 'Post scheduled!' ),
	};

I'll plan to create a separate issue.