service instance proxy V2

[wpjunior]

The Tsuru has a way to proxy requests to a backend of service instance, nowadays is:

/services/<SERVICE>/proxy/<INSTANCE>?callback=%2Fresources%2F<INSTANCE>%2F<CUSTOM_PATH>

why evolve to a new model?

• repeat on callback querystring is a little redundant
• user could escape to a instance that does not have permission, i. e: /services/<SERVICE>/proxy/instance-a?callback=%2Fresources%2Finstance-b%2Finfo
• simplify clients codebase.

proposal:
new proxy API with same permission model, but with a syntax sugar:

/1.20/services/<SERVICE>/resources/<INSTANCE>/<CUSTOM_PATH>

this model ensure easy way to interoperate trough tsuru api and directly access.

ex:

• trough tsuru api: http://mytsuru.com/1.20/services/myservice/resources/instance/info
• direct access: http://myservicebackend.com/resources/instance/info