#1493 - CreatePostMutation should not allow contributors to publish posts

[jasonbahl]

What does this implement/fix? Explain your changes.

According to WordPress role definitions, Contributors can write and manage their own posts, but cannot publish them.

Currently, WPGraphQL allows contributors to publish posts.

This PR prevents users without publish_posts capability from publishing. If the mutation is set to publish, future or private, the status defaults to pending instead.

Does this close any currently open issues?

closes #1493

Any relevant logs, error output, GraphiQL screenshots, etc?

Mutation executed as a Contributor.

[codecov]

Codecov Report

Merging #1499 into develop will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop    #1499      +/-   ##
===========================================
- Coverage    59.04%   59.04%   -0.01%     
===========================================
  Files          192      192              
  Lines        11270    11309      +39     
===========================================
+ Hits          6654     6677      +23     
- Misses        4616     4632      +16     

Impacted Files	Coverage Δ
src/Mutation/PostObjectCreate.php	62.85% <100.00%> (+0.42%)	⬆️
src/Admin/Settings/Settings.php	0.00% <0.00%> (ø)
src/Type/Object/PostObject.php	57.27% <0.00%> (+0.39%)	⬆️
access-functions.php	61.33% <0.00%> (+1.33%)	⬆️
src/Type/Object/TermObject.php	76.92% <0.00%> (+1.92%)	⬆️
src/Request.php	59.37% <0.00%> (+3.30%)	⬆️

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[duffn]

LGTM.