Restrict the Try Gutenberg callout audience

[pento]

As exciting as it would be to put Gutenberg in front of every WordPress users on the planet, we can start a little smaller, and ramp up in future releases.

To begin with, let's go with these categories:

• When Gutenberg is either not installed, or not activated, only show the callout to users with the install_plugins capability.
• When Gutenberg is activated, expand that to include all users with the edit_posts capability.

[danieltj]

I'm not being sarcastic or insincere here; thank you for this. I'm very pleased to see this issue addressed.

It concerned me a lot, the possibility of showing the callout to everyone.

For context: #44670

[pento]

44680.diff​ is ready for commit with sign off from another committer.

[jorbin]

In 43543:

Gutenberg: Restrict "Try Gutenberg" based on capability and gutenstatus

When Gutenberg is either not installed, or not activated, only show the callout to users with the install_plugins capability.
When Gutenberg is activated, expand that to include all users with the edit_posts capability.

Props pento.
Fixes #44680.

[jorbin]

In 43544:

Gutenberg: Restrict "Try Gutenberg" based on capability and gutenstatus

When Gutenberg is either not installed, or not activated, only show the callout to users with the install_plugins capability.
When Gutenberg is activated, expand that to include all users with the edit_posts capability.

4.9 branch commit.

Props pento.
Fixes #44680.

[jorbin]

In 43545:

Gutenbeg: you can't remove call outs that don't exist

This commit should have just gone into the 4.9 branch. It did in [43544].

See: #44680
Unprops jorbin
props ocean90