Automatic resubscription when logged in using jwt property

[Shiranuit]

What does this PR do ?

This PR enables the automatic resubscription of the SDK when logged in using the JWT property

[codecov]

Codecov Report

Merging #657 (19b2523) into 7-dev (1f04b94) will increase coverage by 0.03%.
The diff coverage is 80.00%.

❗ Current head 19b2523 differs from pull request most recent head df9c5b4. Consider uploading reports for the commit df9c5b4 to get more accurate results

@@            Coverage Diff             @@
##            7-dev     #657      +/-   ##
==========================================
+ Coverage   85.65%   85.68%   +0.03%     
==========================================
  Files          36       36              
  Lines        1708     1712       +4     
  Branches      309      311       +2     
==========================================
+ Hits         1463     1467       +4     
  Misses        183      183              
  Partials       62       62              

Impacted Files	Coverage Δ
src/Kuzzle.ts	85.75% <80.00%> (+0.17%)	⬆️

---

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 1f04b94...df9c5b4. Read the comment docs.

[xbill82]

shouldn't this be a getter checking the existence of this.auth.authenticationToken instead of a static member synced by another setter?

[Shiranuit]

I can't because in cookieAuth mode there is no JWT property set but that doesn't mean the SDK is not logged in, that's why I cannot always check if there is a JWT but I can set a property when people do want to put a JWT by hand.