Allow experience-cs admin to set project identifier

To achieve this, I've had to remove the explicit *overriding* of
`Project#identifier` in `Project::Create.build_project`. Now it only
sets the identifier if none is provided. Even this isn't strictly
necessary, because of the `Project#check_unique_not_null` check
which is triggered on a `before_validation` callback. However, I want to
keep the changes to a minimum to reduce the risk of breaking anything
and, in any case, I'm not very convinced about the existence of that
`before_validation`, so I'd prefer not to increase reliance on it.

Author: floehopper

lib/concepts/project/operations/create.rb

@@ -17,8 +17,8 @@ def call(project_hash:)
       private
 
       def build_project(project_hash)
-        identifier = PhraseIdentifier.generate
-        new_project = Project.new(project_hash.except(:components).merge(identifier:))
+        project_hash[:identifier] ||= PhraseIdentifier.generate
+        new_project = Project.new(project_hash.except(:components))
         new_project.components.build(project_hash[:components])
         new_project
       end

spec/features/project/creating_a_project_spec.rb

@@ -213,6 +213,7 @@
     let(:params) do
       {
         project: {
+          identifier: 'test-project',
           name: 'Test Project',
           locale: 'fr',
           project_type: Project::Types::SCRATCH,
@@ -230,6 +231,13 @@
       expect(response).to have_http_status(:created)
     end
 
+    it 'sets the project identifier to the specified (not the generated) value' do
+      post('/api/projects', headers:, params:)
+      data = JSON.parse(response.body, symbolize_names: true)
+
+      expect(data[:identifier]).to eq('test-project')
+    end
+
     it 'sets the project name to the specified value' do
       post('/api/projects', headers:, params:)
       data = JSON.parse(response.body, symbolize_names: true)