Add feature spec for edit Release page

This commits adds an RSpec feature spec for the recently-added "Edit
Release" page.

spec/features/projects/releases/user_views_edit_release_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe 'User edits Release', :js do
+  let_it_be(:project) { create(:project, :repository) }
+  let_it_be(:release) { create(:release, project: project, name: 'The first release' ) }
+  let_it_be(:user) { create(:user) }
+
+  before do
+    project.add_developer(user)
+
+    gitlab_sign_in(user)
+
+    visit edit_project_release_path(project, release)
+  end
+
+  def fill_out_form_and_click(button_to_click)
+    fill_in 'Release title', with: 'Updated Release title'
+    fill_in 'Release notes', with: 'Updated Release notes'
+
+    click_button button_to_click
+
+    wait_for_requests
+  end
+
+  it 'renders the breadcrumbs' do
+    within('.breadcrumbs') do
+      expect(page).to have_content("#{project.creator.name} #{project.name} Edit Release")
+
+      expect(page).to have_link(project.creator.name, href: user_path(project.creator))
+      expect(page).to have_link(project.name, href: project_path(project))
+      expect(page).to have_link('Edit Release', href: edit_project_release_path(project, release))
+    end
+  end
+
+  it 'renders the edit Release form' do
+    expect(page).to have_content('Releases are based on Git tags. We recommend naming tags that fit within semantic versioning, for example v1.0, v2.0-pre.')
+
+    expect(find_field('Tag name', { disabled: true }).value).to eq(release.tag)
+    expect(find_field('Release title').value).to eq(release.name)
+    expect(find_field('Release notes').value).to eq(release.description)
+
+    expect(page).to have_button('Save changes')
+    expect(page).to have_button('Cancel')
+  end
+
+  it 'redirects to the main Releases page without updating the Release when "Cancel" is clicked' do
+    original_name = release.name
+    original_description = release.description
+
+    fill_out_form_and_click 'Cancel'
+
+    expect(current_path).to eq(project_releases_path(project))
+
+    release.reload
+
+    expect(release.name).to eq(original_name)
+    expect(release.description).to eq(original_description)
+  end
+
+  it 'updates the Release and redirects to the main Releases page when "Save changes" is clicked' do
+    fill_out_form_and_click 'Save changes'
+
+    expect(current_path).to eq(project_releases_path(project))
+
+    release.reload
+
+    expect(release.name).to eq('Updated Release title')
+    expect(release.description).to eq('Updated Release notes')
+  end
+end