Change SSE route structure

Contributes to https://gitlab.com/gitlab-org/gitlab/-/issues/213282

We want to migrate URIs route structure from
`gitlab.com/[namespace]/[project]/-/sse/[editable]` to
`gitlab.com/[namespace]/[project]/-/sse/[editable]/-/success`.

changelogs/unreleased/213282-add-support-for-vue-routes.yml

+---
+title: Add vue routes support to Static Site Editor
+merge_request: 30163
+author:
+type: added

config/routes/repository_scoped.rb

@@ -31,9 +31,9 @@ scope format: false do
     resources :protected_branches, only: [:index, :show, :create, :update, :destroy, :patch], constraints: { id: Gitlab::PathRegex.git_reference_regex }
     resources :protected_tags, only: [:index, :show, :create, :update, :destroy]
 
-    scope constraints: { id: /[^\0]+/ } do
+    scope constraints: { id: /[^\0]+?/ } do
       scope controller: :static_site_editor do
-        get '/sse/*id', action: :show, as: :show_sse
+        get '/sse/:id(/*vueroute)', action: :show, as: :show_sse
       end
     end
   end

spec/controllers/projects/static_site_editor_controller_spec.rb

@@ -58,6 +58,11 @@ describe Projects::StaticSiteEditorController do
             expect(assigns(:config)).to be_a(Gitlab::StaticSiteEditor::Config)
           end
 
+          it 'correctly assigns ref and path' do
+            expect(assigns(:ref)).to eq('master')
+            expect(assigns(:path)).to eq('README.md')
+          end
+
           context 'when combination of ref and file path is incorrect' do
             let(:default_params) { super().merge(id: 'unknown') }
 

spec/routing/project_routing_spec.rb

@@ -822,8 +822,10 @@ describe 'project routing' do
 
   describe Projects::StaticSiteEditorController, 'routing' do
     it 'routes to static_site_editor#show', :aggregate_failures do
-      expect(get('/gitlab/gitlabhq/-/sse/master/CONTRIBUTING.md')).to route_to('projects/static_site_editor#show', namespace_id: 'gitlab', project_id: 'gitlabhq', id: 'master/CONTRIBUTING.md')
-      expect(get('/gitlab/gitlabhq/-/sse/master/README')).to route_to('projects/static_site_editor#show', namespace_id: 'gitlab', project_id: 'gitlabhq', id: 'master/README')
+      expect(get('/gitlab/gitlabhq/-/sse/master%2FCONTRIBUTING.md')).to route_to('projects/static_site_editor#show', namespace_id: 'gitlab', project_id: 'gitlabhq', id: 'master/CONTRIBUTING.md')
+      expect(get('/gitlab/gitlabhq/-/sse/master%2FCONTRIBUTING.md/')).to route_to('projects/static_site_editor#show', namespace_id: 'gitlab', project_id: 'gitlabhq', id: 'master/CONTRIBUTING.md')
+      expect(get('/gitlab/gitlabhq/-/sse/master%2FREADME/unsupported/error')).to route_to('projects/static_site_editor#show', namespace_id: 'gitlab', project_id: 'gitlabhq', id: 'master/README', vueroute: 'unsupported/error')
+      expect(get('/gitlab/gitlabhq/-/sse/master%2Flib%2FREADME/success')).to route_to('projects/static_site_editor#show', namespace_id: 'gitlab', project_id: 'gitlabhq', id: 'master/lib/README', vueroute: 'success')
     end
   end