Allow meta tags to be configured from within Page Manager UI

Hey, i made the first patch for this new feature. There's still some ways to improve, but for a first patch I believe this is good :)

Thank you for putting that together. Let's see what the testbot says, just to be safe.

Sorry, the last patch was missing some part of the diff.
The first patch (2988154-4-v122.patch) is a patch to apply in metatag:^1.22, and the second one (2988154-4.patch) to 8.x-1.x-dev.

Hey, i made some changes to make the modal work right in the version 1.22.

I moved the hook to be inside the metatag_page_manager module and created this new patch.
It will work for both 1.22 and 8.x-1.x-dev branches.

I just added a small validation to make the metatags edit button visible only if the user has the "administer meta tags" permission.

Is the permission change useful? Do people want to require the permission be given to users who are editing Page Manager pages in order to also edit the meta tags?

The permission is already necessary if the user wants to edit the metatags because it is the permission for the "entity.metatag_defaults.edit_form" (route used for editing the metatags in this patch).
I'm just hiding the button in case the user doesn't have permission for the route the button would direct him to. :)

Ok, fair point.

I tested the patch and it needs work.

What I was envisioning would be that the Metatag configuration would show up as a link alongside "General", "Contexts", etc in the left sidebar, and would not be a link in the interior area.

Furthermore, when I clicked the link it resulted in an error in the JSON response:

{"message":"The \u0022metatag_defaults\u0022 parameter was not converted for the path \u0022\/admin\/config\/search\/metatag\/{metatag_defaults}\u0022 (route name: \u0022entity.metatag_defaults.edit_form\u0022)"}

Makes sense, I'll work on it.

Hey Damien, the first part is going to take a little longer to implement, so now I'm going to focus on the error you encountered. I was unable to replicate this error in my local environment. Could you provide more information on how to reproduce it?

I was testing with the latest git checkouts for CTools 8.x-3.x and Page Manager 8.x-4.x, I edited the existing node view page, I added a new variant, filled in the initial dialog to give it a name, as soon as I submitted that form it gave a WSOD error because $form['wizard_tree']['#wizard'] was empty. I wrapped that in a quick if(!empty()) (forgot to upload a new patch), then was able to create the variant and get to the point I could see the link. The error logged in #11 was visible in the browser's console when I clicked the "edit" button.

Hey, I'm done fixing the bug you found (and a few others I found during testing), this patch release contains these fixes.

The next step is to move the meta tags option to the correct location, as directed by you, Damien. Soon our team will work on it.

I rerolled patch to 2.0 version

DamienMcKenna can you test it again? I don't see any problem

Update logic came from patch #15, to prevent error regarding missing "wizard_tree" field
more details in the interdiff