[Access] Create draft ws brocker for new PUB/SUB

[Guitarheroua]

TODO

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 4.03458% with 333 lines in your changes missing coverage. Please review.

Project coverage is 40.92%. Comparing base (36f067d) to head (173f141).
Report is 117 commits behind head on master.

Files with missing lines	Patch %	Lines
engine/access/rest/routes/websocket_broker.go	0.00%	219 Missing ⚠️
engine/access/rest/routes/ws_broker_handler.go	0.00%	41 Missing ⚠️
cmd/access/node_builder/access_node_builder.go	0.00%	24 Missing ⚠️
cmd/observer/node_builder/observer_builder.go	0.00%	24 Missing ⚠️
engine/access/rpc/engine.go	9.09%	10 Missing ⚠️
engine/access/rest/routes/router.go	0.00%	8 Missing ⚠️
...utes/subscription_handlers/subscription_handler.go	50.00%	6 Missing ⚠️
cmd/util/cmd/run-script/cmd.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6606      +/-   ##
==========================================
- Coverage   41.14%   40.92%   -0.23%     
==========================================
  Files        2036     2017      -19     
  Lines      179997   178691    -1306     
==========================================
- Hits        74060    73126     -934     
+ Misses      99720    99447     -273     
+ Partials     6217     6118      -99     

Flag	Coverage Δ
unittests	40.92% <4.03%> (-0.23%)	⬇️

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