Add typescript definitions for Auth controller

[Aschen]

What does this PR do?

Adds Typescript support for the AuthController.

I took the descriptions from the documentation.

How should this be manually tested?

Build and pack the SDK: npm run build && npm pack

Then init a Node project and add this dependency:

{
  ...
  "dependencies": {
    "kuzzle-sdk": "file:kuzzle-sdk-7.2.0.tgz"
  }
}

Then create a test.ts file with the following and try to use the controller (just for the auto-completion)

Other changes

Boyscout

[codecov]

Codecov Report

Merging #526 into 7-dev will decrease coverage by 2.37%.
The diff coverage is 87.28%.

@@            Coverage Diff             @@
##            7-dev     #526      +/-   ##
==========================================
- Coverage   95.57%   93.20%   -2.38%     
==========================================
  Files          32       32              
  Lines        1311     1354      +43     
  Branches        0       85      +85     
==========================================
+ Hits         1253     1262       +9     
- Misses         58       72      +14     
- Partials        0       20      +20     

Impacted Files	Coverage Δ
src/core/Room.js	100.00% <ø> (ø)
src/core/security/Role.ts	71.42% <71.42%> (ø)
src/controllers/Auth.ts	75.94% <75.94%> (ø)
src/controllers/Base.ts	88.88% <88.88%> (ø)
src/Kuzzle.ts	87.55% <100.00%> (ø)
src/controllers/Bulk.js	100.00% <100.00%> (ø)
src/controllers/Collection.js	100.00% <100.00%> (ø)
src/controllers/Document.js	95.38% <100.00%> (ø)
src/controllers/Index.js	100.00% <100.00%> (ø)
src/controllers/MemoryStorage.js	96.05% <100.00%> (ø)
... and 24 more

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