Provide a way to log successful and failed requests

[ikhoon]

Motivation:

To diagnose an exception error on the client-side, request logs are important to check request parameters, response duration and application errors.

Modifications:

• Add RequestLogConfig which can limit the sampling rate, adjust target groups, and set the logging levels.
• TransientServiceOption.WITH_SERVICE_LOGGING is specified to HealthCheckService or PrometheusExpositionService if METRICS or HEALTH group is defined in RequestLogConfig

Result:

• Logging configuration example:

  {
    "targetGroups": [ "API", "HEALTH" ],
    "loggerName": "centraldogma.test",
    "requestLogLevel": "DEBUG",
    "successfulResponseLevel": "DEBUG",
    "failureResponseLevel": "ERROR",
    "successSamplingRate": 0.4,
    "failureSamplingRate": 0.6
  }
  

• Fixes #718

[codecov[bot]]

Codecov Report

Merging #719 (5a862e6) into master (f1a1c03) will increase coverage by 0.08%. The diff coverage is 80.00%.

@@             Coverage Diff              @@
##             master     #719      +/-   ##
============================================
+ Coverage     70.31%   70.40%   +0.08%     
- Complexity     3418     3444      +26     
============================================
  Files           349      351       +2     
  Lines         13470    13565      +95     
  Branches       1454     1466      +12     
============================================
+ Hits           9472     9550      +78     
- Misses         3139     3153      +14     
- Partials        859      862       +3     

Impacted Files	Coverage Δ
...linecorp/centraldogma/server/RequestLogConfig.java	47.05% <47.05%> (ø)
...com/linecorp/centraldogma/server/CentralDogma.java	79.36% <94.82%> (+1.90%)	:arrow_up:
...ecorp/centraldogma/server/CentralDogmaBuilder.java	55.03% <100.00%> (+1.07%)	:arrow_up:
...necorp/centraldogma/server/CentralDogmaConfig.java	80.95% <100.00%> (+0.26%)	:arrow_up:
.../linecorp/centraldogma/server/RequestLogGroup.java	100.00% <100.00%> (ø)
...server/internal/thrift/CentralDogmaExceptions.java	50.00% <0.00%> (-13.64%)	:arrow_down:
...centraldogma/server/internal/api/WatchService.java	76.27% <0.00%> (-3.39%)	:arrow_down:
...al/storage/repository/cache/CachingRepository.java	95.31% <0.00%> (+0.78%)	:arrow_up:
.../linecorp/centraldogma/client/AbstractWatcher.java	80.00% <0.00%> (+2.66%)	:arrow_up:
... and 2 more

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[trustin]

• Could a user specify different logging settings for different target groups? For example, a user might want to lower the log level or rate for WEB but not for API.
• Can we also add OTHERS, which is used for all other requests?
• How about categories rather than target groups?