DEV: Absorb onebox gem into core (#12979)

* Move onebox gem in core library

* Update template file path

* Remove warning for onebox gem caching

* Remove onebox version file

* Remove onebox gem

* Add sanitize gem

* Require onebox library in lazy-yt plugin

* Remove onebox web specific code

This code was used in standalone onebox Sinatra application

* Merge Discourse specific AllowlistedGenericOnebox engine in core

* Fix onebox engine filenames to match class name casing

* Move onebox specs from gem into core

* DEV: Rename `response` helper to `onebox_response`

Fixes a naming collision.

* Require rails_helper

* Don't use `before/after(:all)`

* Whitespace

* Remove fakeweb

* Remove poor unit tests

* DEV: Re-add fakeweb, plugins are using it

* Move onebox helpers

* Stub Instagram API

* FIX: Follow additional redirect status codes (#476)

Don’t throw errors if we encounter 303, 307 or 308 HTTP status codes in responses

* Remove an empty file

* DEV: Update the license file

Using the copy from https://choosealicense.com/licenses/gpl-2.0/#

Hopefully this will enable GitHub to show the license UI?

* DEV: Update embedded copyrights

* DEV: Add Onebox copyright notice

* DEV: Add MIT license, convert COPYRIGHT.txt to md

* DEV: Remove an incorrect copyright claim

Co-authored-by: Jarek Radosz <jradosz@gmail.com>
Co-authored-by: jbrw <jamie@goatforce5.org>

lib/onebox/engine/github_issue_onebox.rb

@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+require_relative '../mixins/github_body'
+
+module Onebox
+  module Engine
+    class GithubIssueOnebox
+      #Author Lidlanca 2014
+      include Engine
+      include LayoutSupport
+      include JSON
+      include Onebox::Mixins::GithubBody
+
+      matches_regexp(/^https?:\/\/(?:www\.)?(?:(?:\w)+\.)?github\.com\/(?<org>.+)\/(?<repo>.+)\/issues\/([[:digit:]]+)/)
+      always_https
+
+      def url
+        m = match
+        "https://api.github.com/repos/#{m["org"]}/#{m["repo"]}/issues/#{m["item_id"]}"
+      end
+
+      private
+
+      def match
+        @match ||= @url.match(/^http(?:s)?:\/\/(?:www\.)?(?:(?:\w)+\.)?github\.com\/(?<org>.+)\/(?<repo>.+)\/(?<type>issues)\/(?<item_id>[\d]+)/)
+      end
+
+      def data
+        created_at = Time.parse(raw['created_at'])
+        closed_at = Time.parse(raw['closed_at']) if raw['closed_at']
+        body, excerpt = compute_body(raw['body'])
+        ulink = URI(link)
+
+        {
+          link: @url,
+          title: raw["title"],
+          body: body,
+          excerpt: excerpt,
+          labels: raw["labels"],
+          user: raw['user'],
+          created_at: created_at.strftime("%I:%M%p - %d %b %y %Z"),
+          created_at_date: created_at.strftime("%F"),
+          created_at_time: created_at.strftime("%T"),
+          closed_at: closed_at&.strftime("%I:%M%p - %d %b %y %Z"),
+          closed_at_date: closed_at&.strftime("%F"),
+          closed_at_time: closed_at&.strftime("%T"),
+          closed_by: raw['closed_by'],
+          avatar: "https://avatars1.githubusercontent.com/u/#{raw['user']['id']}?v=2&s=96",
+          domain: "#{ulink.host}/#{ulink.path.split('/')[1]}/#{ulink.path.split('/')[2]}",
+        }
+      end
+    end
+  end
+end