add supernode api for seed pattern

[wangforthinker]

Signed-off-by: allen.wq [email protected]

Ⅰ. Describe what this PR did

Add supernode api for seed pattern.

Ⅱ. Does this pull request fix one issue?

NONE.

Ⅲ. Why don't you add test cases (unit test/integration test)? (你真的觉得不需要加测试吗？)

none.

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[codecov-commenter]

Codecov Report

Merging #1372 into master will decrease coverage by 0.61%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #1372      +/-   ##
==========================================
- Coverage   51.88%   51.26%   -0.62%     
==========================================
  Files         135      135              
  Lines        8803     8908     +105     
==========================================
  Hits         4567     4567              
- Misses       3859     3964     +105     
  Partials      377      377              

Impacted Files	Coverage Δ
dfget/core/api/supernode_api.go	37.85% <0.00%> (-43.86%)	⬇️
dfget/core/helper/test_helper.go	39.79% <0.00%> (-2.14%)	⬇️

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[lowzj]

LGTM