Add support for PlantUML diagrams in Asciidoc.

This MR enables rendering of PlantUML diagrams in Asciidoc documents. To add a
PlantUML diagram all we need is to include a plantuml block like:

```
[plantuml, id="myDiagram", width="100px", height="100px"]
--
bob -> alice : ping
alice -> bob : pong
--
```

The plantuml block is substituted by an HTML img element with *src* pointing to
an external PlantUML server.

This MR also add a PlantUML integration section to the Administrator -> Settings
page to configure the PlantUML rendering service and to enable/disable it.

Closes: #17603

3 files changed, 26 insertions, 0 deletions

diff --git a/db/migrate/20161201001911_add_plant_uml_url_to_application_settings.rb b/db/migrate/20161201001911_add_plant_uml_url_to_application_settings.rb
new file mode 100644
index 00000000000..b8d8742ae40
--- /dev/null
+++ b/db/migrate/20161201001911_add_plant_uml_url_to_application_settings.rb
@@ -0,0 +1,12 @@
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class AddPlantUmlUrlToApplicationSettings < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  def change
+    add_column :application_settings, :plantuml_url, :string
+  end
+end
diff --git a/db/migrate/20161206003819_add_plant_uml_enabled_to_application_settings.rb b/db/migrate/20161206003819_add_plant_uml_enabled_to_application_settings.rb
new file mode 100644
index 00000000000..3677f978cc2
--- /dev/null
+++ b/db/migrate/20161206003819_add_plant_uml_enabled_to_application_settings.rb
@@ -0,0 +1,12 @@
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class AddPlantUmlEnabledToApplicationSettings < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  def change
+    add_column :application_settings, :plantuml_enabled, :boolean
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index f3bf7ced393..c58a886b0fa 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -107,6 +107,8 @@ ActiveRecord::Schema.define(version: 20170106172224) do
     t.integer "housekeeping_full_repack_period", default: 50, null: false
     t.integer "housekeeping_gc_period", default: 200, null: false
     t.boolean "html_emails_enabled", default: true
+    t.string "plantuml_url"
+    t.boolean "plantuml_enabled"
   end
 
   create_table "audit_events", force: :cascade do |t|