add tests for controllers and ActionCable channels; improve main backend docs

main-server/spec/rails_helper.rb

@@ -2,7 +2,7 @@
 if ENV["COVERAGE"]
   require "simplecov"
   SimpleCov.start "rails" do
-    add_filter "/spec/"
+    skip "/spec/"
   end
 end
 require 'spec_helper'
@@ -69,7 +69,7 @@ RSpec.configure do |config|
   # behaviour is considered legacy and will be removed in a future version.
   #
   # To enable this behaviour uncomment the line below.
-  # config.infer_spec_type_from_file_location!
+  config.infer_spec_type_from_file_location!
 
   # Filter lines from Rails gems in backtraces.
   config.filter_rails_from_backtrace!