Improve ContextualLinkInterface doxygen

Thanks! Good idea to add more information here...

But when I read this:

+++ b/core/lib/Drupal/Core/Menu/ContextualLinkInterface.php
@@ -9,6 +9,14 @@
+ * file. These YAML files contain a list of plugin definitions keyed by the
+ * plugin id. Each definition / link must define a route_name and a group

I went ... Really? I don't see any plugin definitions or plugin IDs there, or if they are, it isn't obvious. They're things like:

block_content.block_edit:
  title: 'Edit'
  group: block_content
  route_name: 'entity.block_content.canonical'

To me, "plugin definition" is a class...

I guess I see what you mean here but when I read that I went uh, what?

Let's see. What can we say. How about this:

These YAML files contain contextual link entries, keyed by an ID. Each entry gives the properties of an implicit contextual link plugin, as defined by this interface, with the ID being the plugin ID.

How about that to replace that sentence that begins with "These YAML files" in this patch?

Sorry, never updated issue status on this. Should we still fix this?

1. +++ b/core/lib/Drupal/Core/Menu/ContextualLinkInterface.php
   @@ -9,6 +9,14 @@
   + * file. These YAML files contain a list of plugin definitions keyed by the
   + * plugin id. Each definition / link must define a route_name and a group
   

   Fair enough, yes I see what you mean -- these are actually plugin definitions... How about wording something like this:

   These YAML files contain a list of contextual link plugin definitions, keyed by plugin ID. Each definition must define....

2. +++ b/core/lib/Drupal/Core/Menu/ContextualLinkInterface.php
   @@ -9,6 +9,14 @@
   + * and might define title, options and weight. See the getter methods on this
   

   Needs comma before "and".

Hello, I have tried to made some changes as commented by @jhodgdon. Please review it.

Hi jhodgdon ,
Thank you for suggestion .I have made the changes accordingly.

Neither the patch in #5 nor the patch in #8 really did what was suggested in #4. Please try again.

Also by the way you need to say "ID" not "id", which I forgot to mention in #4.

And all documentation lines should be wrapped as close to 80 characters as possible without going over.

Hi!
I hope I got this right.
FYI, I made a slight change (grammatically it should be more correct): modulename.links.contextual.yml to module_name.links.contextual.yml

This looks great to me, thanks!

Committed/pushed to 8.1.x and cherry-picked to 8.0.x. Thanks!