Add jira installations controller

This controller is responding with JSON only.
It will be used to set Jira Connect up for an
self-managed instance.

app/controllers/jira_connect/installations_controller.rb

+# frozen_string_literal: true
+
+class JiraConnect::InstallationsController < JiraConnect::ApplicationController
+  def index
+    render json: installation_json(current_jira_installation)
+  end
+
+  def update
+    if current_jira_installation.update(installation_params)
+      render json: installation_json(current_jira_installation)
+    else
+      render(
+        json: { errors: current_jira_installation.errors },
+        status: :unprocessable_entity
+      )
+    end
+  end
+
+  private
+
+  def installation_json(installation)
+    {
+      gitlab_com: installation.instance_url.blank?,
+      instance_url: installation.instance_url
+    }
+  end
+
+  def installation_params
+    params.require(:installation).permit(:instance_url)
+  end
+end

config/routes/jira_connect.rb

@@ -14,4 +14,10 @@ namespace :jira_connect do
 
   resources :subscriptions, only: [:index, :create, :destroy]
   resources :branches, only: [:new]
+
+  resources :installations, only: [:index] do
+    collection do
+      put :update
+    end
+  end
 end

spec/requests/jira_connect/installations_controller_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe JiraConnect::InstallationsController do
+  let_it_be(:installation) { create(:jira_connect_installation) }
+
+  describe 'GET /-/jira_connect/installations' do
+    before do
+      get '/-/jira_connect/installations', params: { jwt: jwt }
+    end
+
+    context 'without JWT' do
+      let(:jwt) { nil }
+
+      it 'returns 403' do
+        expect(response).to have_gitlab_http_status(:forbidden)
+      end
+    end
+
+    context 'with valid JWT' do
+      let(:qsh) { Atlassian::Jwt.create_query_string_hash('https://gitlab.test/installations', 'GET', 'https://gitlab.test') }
+      let(:jwt) { Atlassian::Jwt.encode({ iss: installation.client_key, qsh: qsh }, installation.shared_secret) }
+
+      it 'returns status ok' do
+        expect(response).to have_gitlab_http_status(:ok)
+      end
+
+      it 'returns the installation as json' do
+        expect(json_response).to eq({
+          'gitlab_com' => true,
+          'instance_url' => nil
+        })
+      end
+
+      context 'with instance_url' do
+        let_it_be(:installation) { create(:jira_connect_installation, instance_url: 'https://example.com') }
+
+        it 'returns the installation as json' do
+          expect(json_response).to eq({
+            'gitlab_com' => false,
+            'instance_url' => 'https://example.com'
+          })
+        end
+      end
+    end
+  end
+
+  describe 'PUT /-/jira_connect/installations' do
+    before do
+      put '/-/jira_connect/installations', params: { jwt: jwt, installation: { instance_url: update_instance_url } }
+    end
+
+    let(:update_instance_url) { 'https://example.com' }
+
+    context 'without JWT' do
+      let(:jwt) { nil }
+
+      it 'returns 403' do
+        expect(response).to have_gitlab_http_status(:forbidden)
+      end
+    end
+
+    context 'with valid JWT' do
+      let(:qsh) { Atlassian::Jwt.create_query_string_hash('https://gitlab.test/subscriptions', 'GET', 'https://gitlab.test') }
+      let(:jwt) { Atlassian::Jwt.encode({ iss: installation.client_key, qsh: qsh }, installation.shared_secret) }
+
+      it 'returns 200' do
+        expect(response).to have_gitlab_http_status(:ok)
+      end
+
+      it 'updates the instance_url' do
+        expect(json_response).to eq({
+          'gitlab_com' => false,
+          'instance_url' => 'https://example.com'
+        })
+      end
+
+      context 'invalid URL' do
+        let(:update_instance_url) { 'invalid url' }
+
+        it 'returns 422 and errors', :aggregate_failures do
+          expect(response).to have_gitlab_http_status(:unprocessable_entity)
+          expect(json_response).to eq({
+            'errors' => {
+              'instance_url' => [
+                'is blocked: Only allowed schemes are http, https'
+              ]
+            }
+          })
+        end
+      end
+    end
+  end
+end