public namespaces only allow properties format

[nobodyiam]

What's the purpose of this PR

public namespaces only allow properties format

Which issue(s) this PR fixes:

Fixes #3119

Brief changelog

check the namespace's isPublic property and set the format to properties if isPublic is true.

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[codecov-commenter]

Codecov Report

Merging #3140 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##             master    #3140   +/-   ##
=========================================
  Coverage     51.24%   51.24%           
- Complexity     2235     2236    +1     
=========================================
  Files           432      432           
  Lines         13425    13427    +2     
  Branches       1381     1382    +1     
=========================================
+ Hits           6879     6881    +2     
  Misses         6068     6068           
  Partials        478      478           

Impacted Files	Coverage Δ	Complexity Δ
...ork/apollo/portal/service/AppNamespaceService.java	75.55% <100.00%> (+0.55%)	22.00 <0.00> (+1.00)

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