Merge branch '20121-add-a-new-have_html_escaped_body_text-matcher' into 'master'

Add a new have_html_escaped_body_text that match an HTML-escaped text

Closes #20121

See merge request !10015

spec/support/matchers/email_matchers.rb

+RSpec::Matchers.define :have_html_escaped_body_text do |expected|
+  match do |actual|
+    expect(actual).to have_body_text(ERB::Util.html_escape(expected))
+  end
+end