add ucdn product

[yufeiminds]

FEATURE:

• Add UCDN product

[codecov-io]

Codecov Report

Merging #17 into master will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff           @@
##           master      #17   +/-   ##
=======================================
  Coverage   96.16%   96.16%           
=======================================
  Files          18       18           
  Lines         521      521           
=======================================
  Hits          501      501           
  Misses         20       20

Impacted Files	Coverage Δ
ucloud/core/client/_client.py	98.66% <0%> (ø)	⬆️

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