[Access] Changed max subscription error code to 429

[Guitarheroua]

In this PR the error code for max subscriptions reached was changed from 503 to 429, as this is not a server error, but more server limitation.

See context here

Closes #7177

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 41.25%. Comparing base (1739d1d) to head (7b679d3).

Files with missing lines	Patch %	Lines
engine/access/rest/websockets/controller.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7158      +/-   ##
==========================================
- Coverage   41.25%   41.25%   -0.01%     
==========================================
  Files        2170     2170              
  Lines      190109   190109              
==========================================
- Hits        78435    78431       -4     
- Misses     105128   105131       +3     
- Partials     6546     6547       +1     

Flag	Coverage Δ
unittests	41.25% <0.00%> (-0.01%)	⬇️

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[peterargue]

is there a test case that covers this? If not we should add one.

[illia-malachyn]

is there a test case that covers this? If not we should add one.

Yes, there is. I updated the PR

[illia-malachyn]

@peterargue I added this to the board (even though it is a PR) because I guess we forgot about this one

[illia-malachyn]

Created a separate issue for this