Fix subscribe crash on user notifications

[samniisan]

Introduces

• Fix crash when receiving a UserNotification (no requestId on this particular Notification type) (sub/unsub in|out|all)
• Fix crash when receiving Notifications whitout any volatile
• Allow chaining in setters of RoomOptions

Boyscoot

• Fix invalid exception messages

[codecov-io]

Codecov Report

Merging #140 into 3.x will decrease coverage by 0.06%. The diff coverage is 45.45%.

@@            Coverage Diff            @@
##              3.x    #140      +/-   ##
=========================================
- Coverage   91.27%   91.2%   -0.07%     
=========================================
  Files          33      33              
  Lines        4697    4697              
  Branches      435     437       +2     
=========================================
- Hits         4287    4284       -3     
  Misses        287     287              
- Partials      123     126       +3

Impacted Files	Coverage Δ
.../io/kuzzle/sdk/responses/NotificationResponse.java	21.27% <0%> (-2.13%)	:arrow_down:
src/main/java/io/kuzzle/sdk/core/Collection.java	93.3% <100%> (ø)	:arrow_up:
src/main/java/io/kuzzle/sdk/core/Room.java	92.03% <33.33%> (-1%)	:arrow_down:
src/main/java/io/kuzzle/sdk/core/RoomOptions.java	71.42% <40%> (ø)	:arrow_up:

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