Fix Backend API mapping rules injected into the proxy config

[guicassolato]

Which issue(s) this PR fixes

Backend api mapping rules injected in the proxy config have two problems:

1. It does not prepend the backend API config path to the pattern of the proxy rule
2. It does not inject the full system_name of the metric but only the part without the .#{backend_api.id} suffix

First problem is due to draper's delegate_all method used in

porta/app/decorators/application_decorator.rb

Line 4 in ccc776c

delegate_all

. This method makes the decorator class to dynamically define delegations of the decorated object's instance methods to the object itself, thus making ProxyRuleDecorator#pattern to execute only once and then always be delegated to the object.

See drapergem/draper#818

The second problem is because of

porta/app/lib/backend_api_logic/metric_extension.rb

Lines 13 to 15 in ccc776c

	def system_name
	attributes['system_name'].to_s.gsub(/#{Regexp.escape(SYSTEM_NAME_SUFFIX_SEPARATOR)}\d+\z/, '')
	end

What this PR does

• Fix path of Backend API mapping rules injected into the proxy config
• Fix system_name of Backend API mapping rules injected into the proxy config

Verification steps

1. Generate a json proxy config file of a product using 2+ backend APIs containing proxy rules
2. Verify that all backend API proxy rules include the proper backend api config's path prepended to the rule's pattern
3. Verify that all backend API proxy rules have the .#{backend_api.id} suffix appended to the end of metric_system_name

[hallelujah]

LGTM
Draper has a bug with collections drapergem/draper#818
Thank you!