spec: better split spec_helper and rails_helper

This fixes the

> DEPRECATION WARNING: Initialization autoloaded the constants ActionText::ContentHelper and ActionText::TagHelper.

error appearing when running specs.

It also gets us closer from a newly-generated rails config.

spec/support/capybara.rb

@@ -0,0 +1,49 @@
+require 'capybara/rspec'
+require 'capybara-screenshot/rspec'
+require 'capybara/email/rspec'
+require 'selenium/webdriver'
+
+Capybara.javascript_driver = :headless_chrome
+Capybara.ignore_hidden_elements = false
+
+Capybara.register_driver :chrome do |app|
+  Capybara::Selenium::Driver.new(app, browser: :chrome)
+end
+
+Capybara.register_driver :headless_chrome do |app|
+  options = Selenium::WebDriver::Chrome::Options.new
+  options.add_argument('--headless')
+  options.add_argument('--window-size=1440,900')
+
+  capabilities = Selenium::WebDriver::Remote::Capabilities.chrome(
+    chromeOptions: { args: ['disable-dev-shm-usage', 'disable-software-rasterizer', 'mute-audio', 'window-size=1440,900'] }
+  )
+
+  download_path = Capybara.save_path
+  # Chromedriver 77 requires setting this for headless mode on linux
+  # Different versions of Chrome/selenium-webdriver require setting differently - just set them all
+  options.add_preference('download.default_directory', download_path)
+  options.add_preference(:download, default_directory: download_path)
+
+  Capybara::Selenium::Driver.new(app,
+    browser: :chrome,
+    desired_capabilities: capabilities,
+    options: options).tap do |driver|
+    # Set download dir for Chrome < 77
+    driver.browser.download_path = download_path
+  end
+end
+
+# FIXME: remove this line when https://github.com/rspec/rspec-rails/issues/1897 has been fixed
+Capybara.server = :puma, { Silent: true }
+
+Capybara.default_max_wait_time = 2
+
+# Save a snapshot of the HTML page when an integration test fails
+Capybara::Screenshot.autosave_on_failure = true
+# Keep only the screenshots generated from the last failing test suite
+Capybara::Screenshot.prune_strategy = :keep_last_run
+# Tell Capybara::Screenshot how to take screenshots when using the headless_chrome driver
+Capybara::Screenshot.register_driver :headless_chrome do |driver, path|
+  driver.browser.save_screenshot(path)
+end