Use BaseController class for controllers

[Aschen]

What does this PR do?

I'm not sure if this is a new feature or an enhancement

This PR intend to unify the way we add/use controllers with the SDK. In this way we can have the same API when using our core controllers (document, collection, etc.) and custom controllers made by users.

All existing controllers are now inheriting from the BaseController class and they are added to the SDK with Kuzzle.useController instead of been manually instantiated.

Example of custom controller

class TaxiController extends BaseController {
  constructor (kuzzle) {
    super(kuzzle, 'my-plugin/taxi');
  }

  startDuty (driver) {
    return this.query({ driver, action: 'startDuty' });
  }
}

kuzzle.useController(TaxiController, 'taxi');

kuzzle.taxi.startDuty('Martin');

I know this look like a breaking change but since we never documented this feature by now it is not really one.

Documentation kuzzleio/documentation#284

How should this be manually tested?

• Step 1 : Run unit tests

[codecov-io]

Codecov Report

Merging #388 into 6-dev will increase coverage by <.01%.
The diff coverage is 99.33%.

@@            Coverage Diff             @@
##            6-dev     #388      +/-   ##
==========================================
+ Coverage   96.65%   96.65%   +<.01%     
==========================================
  Files          30       30              
  Lines        1435     1437       +2     
==========================================
+ Hits         1387     1389       +2     
  Misses         48       48

Impacted Files	Coverage Δ
src/controllers/index.js	97.29% <100%> (ø)	⬆️
src/controllers/bulk.js	100% <100%> (ø)	⬆️
src/Kuzzle.js	95.45% <100%> (+0.04%)	⬆️
src/controllers/server.js	100% <100%> (ø)	⬆️
src/controllers/collection.js	94.8% <100%> (ø)	⬆️
src/controllers/realtime/index.js	100% <100%> (ø)	⬆️
src/controllers/memoryStorage.js	96.25% <100%> (ø)	⬆️
src/controllers/base.js	100% <100%> (ø)	⬆️
src/controllers/auth.js	93.02% <100%> (ø)	⬆️
src/controllers/security/index.js	99.58% <100%> (ø)	⬆️
... and 1 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 9aba3cc...f5eb3cd. Read the comment docs.

[scottinet]

I like the idea (and this looks more like an enhancement than a new feature to me), but I disagree with the actions exposure being implicit.

I would prefer that you add an init function (possibly returning a promise?) that explicitly declares what actions can be performed for that registering controller.
Or any other method of your choice, as long as it's explicit. :)

[Aschen]

@scottinet I didn't understand what you mean by explicitly declare what actions can be performed for that registering controller. Since the controller is a class, is not the SDK responsibility to allow or disallow method calling. If we weren't in JS, we would have the private keyword but..

I could wrap the controller class with a Proxy or something but I didn't really see the point here.

[scottinet]

@Aschen > You have a point.
Just to explain myself: we had to make actions exposure explicit in Kuzzle's controllers to prevent internal methods from being leaked to the API. And I erroneously thought that we had possibly the same problem here, while it's obvious that the context is different.