Move component state to Redux store

[chuckharmston]

In most cases, things you'd consider storing as component-level state may be helpful for other components to know. For example:

testpilot/frontend/src/app/components/MainInstallButton.js

Line 11 in 622e528

isInstalling: false

We currently store isInstalling on the install button's component. If this is stored in the Redux store, the email modal component would be able to monitor its value and pop up whenever it changes from false to true, rather than needing to be manually-triggered.

There's a lot of good discussion about this out there:

reduxjs/redux#1287
http://redux.js.org/docs/FAQ.html#do-i-have-to-put-all-my-state-into-redux-should-i-ever-use-reacts-setstate

There is one important benefit to everything going into the Redux store: it turns your app into a finite state machine. The Redux store becomes the input, and the output is the rendered DOM. This makes some good things easy: testing complex interactions between components, time travel, bug reproduction, and testing.

For the sake of being consistent and explicit, I'd suggest implementing a guideline to not use component state, instead putting everything into the Redux store and passing values down as props.

[johngruen]

we should do this at some point.

[chuckharmston]

For a less contrived example of how this might be useful, see the addon.restart store bits in #1369.

[fzzzy]

I think this is mostly done now: as you can see here https://github.com/mozilla/testpilot/blob/master/frontend/src/app/reducers/addon.js RestartState.isRequired is part of the AddonState in redux now, and here https://github.com/mozilla/testpilot/blob/master/frontend/src/app/reducers/experiments.js you can see that inProgress is now a part of the Experiment redux state.

However, an anti-example is https://github.com/mozilla/testpilot/blob/master/frontend/src/app/reducers/newsletter-form.js where I think possibly all that state should be local to the component with setState.