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

1 files changed, 15 insertions, 1 deletions

diff --git a/spec/requests/api/settings_spec.rb b/spec/requests/api/settings_spec.rb
index ad9d8a25af4..91e3c333a02 100644
--- a/spec/requests/api/settings_spec.rb
+++ b/spec/requests/api/settings_spec.rb
@@ -16,6 +16,8 @@ describe API::Settings, 'Settings', api: true  do
       expect(json_response['repository_storage']).to eq('default')
       expect(json_response['koding_enabled']).to be_falsey
       expect(json_response['koding_url']).to be_nil
+      expect(json_response['plantuml_enabled']).to be_falsey
+      expect(json_response['plantuml_url']).to be_nil
     end
   end
 
@@ -28,7 +30,8 @@ describe API::Settings, 'Settings', api: true  do
 
       it "updates application settings" do
         put api("/application/settings", admin),
-          default_projects_limit: 3, signin_enabled: false, repository_storage: 'custom', koding_enabled: true, koding_url: 'http://koding.example.com'
+          default_projects_limit: 3, signin_enabled: false, repository_storage: 'custom', koding_enabled: true, koding_url: 'http://koding.example.com',
+          plantuml_enabled: true, plantuml_url: 'http://plantuml.example.com'
         expect(response).to have_http_status(200)
         expect(json_response['default_projects_limit']).to eq(3)
         expect(json_response['signin_enabled']).to be_falsey
@@ -36,6 +39,8 @@ describe API::Settings, 'Settings', api: true  do
         expect(json_response['repository_storages']).to eq(['custom'])
         expect(json_response['koding_enabled']).to be_truthy
         expect(json_response['koding_url']).to eq('http://koding.example.com')
+        expect(json_response['plantuml_enabled']).to be_truthy
+        expect(json_response['plantuml_url']).to eq('http://plantuml.example.com')
       end
     end
 
@@ -47,5 +52,14 @@ describe API::Settings, 'Settings', api: true  do
         expect(json_response['error']).to eq('koding_url is missing')
       end
     end
+
+    context "missing plantuml_url value when plantuml_enabled is true" do
+      it "returns a blank parameter error message" do
+        put api("/application/settings", admin), plantuml_enabled: true
+
+        expect(response).to have_http_status(400)
+        expect(json_response['error']).to eq('plantuml_url is missing')
+      end
+    end
   end
 end