Rest protocol

[Patrick0308]

What this PR does:

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[flycash]

Firstly, it seems that we use the camel case rather than xxx_xxx

[codecov-io]

Codecov Report

Merging #329 into feature/rest will increase coverage by 0.46%.
The diff coverage is 46.15%.

@@               Coverage Diff                @@
##           feature/rest     #329      +/-   ##
================================================
+ Coverage         66.32%   66.78%   +0.46%     
================================================
  Files               127      128       +1     
  Lines              7828     7877      +49     
================================================
+ Hits               5192     5261      +69     
+ Misses             2130     2098      -32     
- Partials            506      518      +12

Impacted Files	Coverage Δ
protocol/rest/rest_protocol.go	93.65% <ø> (ø)	⬆️
protocol/rest/rest_exporter.go	100% <ø> (ø)	⬆️
...l/rest/rest_config_reader/default_config_reader.go	45.45% <100%> (ø)
protocol/rest/rest_config_initializer.go	82.5% <33.33%> (+50.55%)	⬆️
protocol/rest/rest_invoker.go	73.07% <66.66%> (+34.89%)	⬆️
cluster/cluster_impl/base_cluster_invoker.go	62.31% <0%> (-10.15%)	⬇️
cluster/cluster_impl/failback_cluster_invoker.go	78.49% <0%> (-2.16%)	⬇️
registry/etcdv3/registry.go	50.5% <0%> (-1.02%)	⬇️
... and 1 more

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[flycash]

Could you split this method into several smaller methods?