No user context for invocations

[tanoshko]

Issue

There is no way to pass some context between different invocations.
This forces to use ugly cycles of requests in scope of one invocation. And this also fails due to #844.

Please provide API to pass some context from one invocation to another.

Use case example:

paging resource, every response contains link to next page which should be used for next invocation.

[Amacuse]

In order to use mechanism of the Jagger http scenario we have to configure com.griddynamics.jagger.invoker.scenario.JHttpUserScenario objects which will represent future test plan. JHttpUserScenario contains a list of com.griddynamics.jagger.invoker.scenario.JHttpUserScenarioStep objects which will be invoked inside invocation phase. The main issue in our case that we don't know the number of these steps in advance. So we can't use this approach for our 'pagination scenario' case.

There is a need to have such mechanism that allow us to trigger 'invocation' phase based on a previous invocation result. Now we get only one invocation and a loop inside com.griddynamics.jagger.invoker.scenario.JHttpUserScenarioInvoker.

Also for 'pagination scenario' we need to have summary metrics based on each step but not for every step as we have now.

[dlatnikov]

Hi @Amacuse . I've already proposed to configure large number of steps (more than possible in your scenario) and configure stop condition that will interrupt loop over your steps. Have you got any success with this approach?