FIX: Further improvements for plugin list (#24622)

Followup e37fb3042d6f56a27a01614e57bc7029f472b0c9

* Automatically remove the prefix `Discourse ` from all the plugin titles to avoid repetition
* Remove the :discourse_dev: icon from the author. Consider a "By Discourse" with no labels as official
* We add a `label` metadata to plugin.rb
  * Only plugins made by us in `discourse` and `discourse-org` GitHub organizations will show these in the list
* Make the plugin author font size a little smaller
* Make the commit sha look like a link so it's more obvious it goes to the code

Also I added some validation and truncation for plugin metadata
parsing since currently you can put absolutely anything in there
and it will show on the plugin list.

spec/lib/plugin/metadata_spec.rb

@@ -12,6 +12,7 @@ RSpec.describe Plugin::Metadata do
 # url: http://discourse.org
 # required version: 1.3.0beta6+48
 # meta_topic_id: 1234
+# label: experimental
 
 some_ruby
 TEXT
@@ -23,7 +24,8 @@ TEXT
       expect(metadata.contact_emails).to eq("frankz@example.com")
       expect(metadata.url).to eq("http://discourse.org")
       expect(metadata.required_version).to eq("1.3.0beta6+48")
-      expect(metadata.meta_topic_id).to eq("1234")
+      expect(metadata.meta_topic_id).to eq(1234)
+      expect(metadata.label).to eq("experimental")
     end
   end
 
@@ -50,4 +52,40 @@ TEXT
     official("discourse-data-explorer")
     unofficial("babble")
   end
+
+  it "does not support anything but integer for meta_topic_id" do
+    metadata = Plugin::Metadata.parse <<TEXT
+# meta_topic_id: 1234
+TEXT
+
+    expect(metadata.meta_topic_id).to eq(1234)
+
+    metadata = Plugin::Metadata.parse <<TEXT
+# meta_topic_id: t/1234 blah
+TEXT
+
+    expect(metadata.meta_topic_id).to eq(nil)
+  end
+
+  it "truncates long field lengths" do
+    metadata = Plugin::Metadata.parse <<TEXT
+# name: #{"a" * 100}
+# about: #{"a" * 400}
+# authors: #{"a" * 300}
+# contact_emails: #{"a" * 300}
+# url: #{"a" * 600}
+# label: #{"a" * 100}
+# required_version: #{"a" * 1500}
+TEXT
+
+    expect(metadata.name.length).to eq(Plugin::Metadata::MAX_FIELD_LENGTHS[:name])
+    expect(metadata.about.length).to eq(Plugin::Metadata::MAX_FIELD_LENGTHS[:about])
+    expect(metadata.authors.length).to eq(Plugin::Metadata::MAX_FIELD_LENGTHS[:authors])
+    expect(metadata.contact_emails.length).to eq(
+      Plugin::Metadata::MAX_FIELD_LENGTHS[:contact_emails],
+    )
+    expect(metadata.url.length).to eq(Plugin::Metadata::MAX_FIELD_LENGTHS[:url])
+    expect(metadata.label.length).to eq(Plugin::Metadata::MAX_FIELD_LENGTHS[:label])
+    expect(metadata.required_version.length).to eq(1000)
+  end
 end