Amend plugin link for Link Manager error.

[tw2113]

Right now, if a user tries to visit the legacy link management pages, they are instructed to install the "Link Manager" plugin which re-enables the pages.

However, the link provided to install the plugin just points to a search by keyword for "Link Manager", which at present time returns 2,153 results to sift through to hopefully find the intended ​https://wordpress.org/plugins/link-manager/

Let's help the user out by providing direct links to install the plugin, if able to, and then if they re-visit the same page without having activated yet, provide a link to activate it too.

Attached is a patch that checks the current status of "Link Manager" plugin, and amends the messaging link URLs to either install or activate the plugin.

[peterwilsoncc]

Thanks for the patch, a couple of minor notes:

• short array syntax in the plugins_api(), Core uses the long array syntax

• If the plugin is installed, I don't think there needs to be a check for the latest version before activating: site admins can handle that as part of their regular update routine

• I may be wrong about the above ;) -- if that's the case and the plugin needs updating a "please update" if condition will be needed. As is, an out of date plugin shows the message 'Sorry, you are not allowed to edit the links for this site.'

This is so much nicer than the current search link. Thanks boss.

[tw2113]

Will fix up the array syntax soon.

I will also look things over and see how to only do some parts if the plugin is installed already.

[tw2113]

Removed the latest version check because in brief hindsight, it was needless. We just need to activate once we get to that point.

Short array syntax removed.

[SergeyBiryukov]

Thanks for the patch!

Just noting that we'd probably want for the approach here to be consistent with the checks for Classic Editor plugin​ in do_block_editor_incompatible_meta_box().

[tw2113]

Thanks @SergeyBiryukov

I will check that section out and further amend to fit. Stay tuned.

[tw2113]

Amended to better match how Classic Editor does its own checks, as opposed to pinging WordPress.org for a status check.

[SergeyBiryukov]

In 51011:

Administration: Improve the message about installing the Link Manager plugin to use legacy Links screen.

This provides direct links to install and activate the plugin, if the user has the capabilities to do so, instead of just linking to plugin search results.

It also matches more closely the message about installing the Classic Editor plugin for meta boxes incompatible with the block editor.

Follow-up to [22855], [44280], [45657].

Props tw2113, peterwilsoncc, SergeyBiryukov.
Fixes #52669.