To help improve shenyu-common module code test coverage

[David Liu <he...@apache.org>]

Hi all,
    Below is the class that need to improve test coverage in shenyu-common
module.

org.apache.shenyu.common.healthcheck.HealthCheckTask(0%)
org.apache.shenyu.common.enums.RpcTypeEnum(0%)
org.apache.shenyu.common.enums.RpcTypeEnum(0%)
org.apache.shenyu.common.enums.RateLimitEnum(0%)
org.apache.shenyu.common.enums.AdminPluginOperateEnum(0%)
org.apache.shenyu.common.enums.AdminResourceEnum(0%)
org.apache.shenyu.common.enums.PluginTypeEnum(0%)
org.apache.shenyu.common.enums.WafEnum(0%)
org.apache.shenyu.common.enums.ParamTypeEnum(line coverage 100%, key branch
coverage missing 25%)
org.apache.shenyu.common.enums.HttpMethodEnum(line coverage 100%, key
branch coverage missing 25%)
org.apache.shenyu.common.dto.convert.Resilience4JHandle(0%)
org.apache.shenyu.common.dto.convert.SentinelHandle(0%)
org.apache.shenyu.common.dto.convert.RequestHandle(0%)
org.apache.shenyu.common.dto.convert.HystrixHandle(0%)
org.apache.shenyu.common.dto.convert.RequestHandle.ShenyuRequestParameter(0%)
org.apache.shenyu.common.dto.convert.RequestHandle.ShenyuCookie(0%)
org.apache.shenyu.common.dto.convert.RequestHandle.ShenyuRequestHeader(0%)
org.apache.shenyu.common.dto.convert.HystrixThreadPoolConfig(0%)
org.apache.shenyu.common.dto.convert.ZombieUpstream(0%)
org.apache.shenyu.common.dto.convert.rule.RuleHandle(0%)
org.apache.shenyu.common.utils.ReflectUtils(64%)
org.apache.shenyu.common.utils.GsonUtils(86%)
org.apache.shenyu.common.constant.HttpConstants(0%)
org.apache.shenyu.common.constant.AdminConstants(0%)
org.apache.shenyu.common.constant.ConsulConstants(0%)
org.apache.shenyu.common.constant.ResourceTypeConstants(0%)
org.apache.shenyu.common.constant.RuleHandleConstants(50%)
org.apache.shenyu.common.constant.DubboParamConstants(0%)
org.apache.shenyu.common.constant.NacosPathConstants(0%)
org.apache.shenyu.common.exception.SerializerException(0%)
org.apache.shenyu.common.exception.ShenyuException(30%)
org.apache.shenyu.common.exception.CommonErrorCode(0%)
org.apache.shenyu.common.dto.MetaData(0%)
org.apache.shenyu.common.dto.ConfigData(0%)
org.apache.shenyu.common.dto.convert.rule.impl.ModifyResponseRuleHandle(0%)
org.apache.shenyu.common.dto.convert.rule.impl.ContextMappingHandle(0%)
org.apache.shenyu.common.dto.convert.rule.impl.ParamMappingHandle(0%)


Each line has record a class and the current test coverage is in the
brackets at end of line.

I post the statistic via the jacoco plugin in the maven test lifetime (you
can use mvn test in your local repository, then you can get the result in
maven generate target directory which named site/jacoco, the code coverage
will be present in the static web page index.html).

We hope more developer to participant to impove test coverage, I have
create the issue in this project's github repository,
https://github.com/apache/incubator-shenyu/issues/1827#issue-955403147，welcome
to participant!