feature: add gray operation on Open API

[jieqian]

gray release
gray deletion release
branch merge release
fetch gray release rules
update gray release rules
find branch
create branch
delete branch

[codecov-io]

Codecov Report

Merging #1518 into master will increase coverage by 10.1%.
The diff coverage is 3.33%.

@@             Coverage Diff              @@
##             master    #1518      +/-   ##
============================================
+ Coverage     38.55%   48.65%   +10.1%     
- Complexity      151     1882    +1731     
============================================
  Files            41      394     +353     
  Lines          1092    11419   +10327     
  Branches        138     1172    +1034     
============================================
+ Hits            421     5556    +5135     
- Misses          616     5438    +4822     
- Partials         55      425     +370

Impacted Files	Coverage Δ	Complexity Δ
...ramework/apollo/portal/service/ReleaseService.java	2.38% <0%> (ø)	2 <0> (?)
...ramework/apollo/openapi/util/OpenApiBeanUtils.java	0% <0%> (ø)	0 <0> (?)
...apollo/openapi/dto/OpenGrayReleaseRuleItemDTO.java	0% <0%> (ø)	0 <0> (?)
...pollo/openapi/v1/controller/ReleaseController.java	2.04% <0%> (ø)	1 <0> (?)
...apollo/openapi/dto/NamespaceGrayDelReleaseDTO.java	0% <0%> (ø)	0 <0> (?)
...llo/adminservice/controller/ReleaseController.java	17.3% <0%> (ø)	3 <0> (?)
...p/framework/apollo/portal/api/AdminServiceAPI.java	13.15% <0%> (ø)	1 <0> (?)
.../apollo/portal/service/NamespaceBranchService.java	2.12% <0%> (ø)	1 <0> (?)
...ork/apollo/openapi/dto/OpenGrayReleaseRuleDTO.java	0% <0%> (ø)	0 <0> (?)
...tal/entity/model/NamespaceGrayDelReleaseModel.java	0% <0%> (ø)	0 <0> (?)
... and 355 more

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[coveralls]

Coverage decreased (-0.7%) to 52.43% when pulling 2dba143f8dcfe20694156669a526895cc96a2750 on jieqian:gray_release_4_openapi into e0ba75c on ctripcorp:master.

[nobodyiam]

Thanks!