dynamic config max_subscription_clients

[LeoGuo621]

• Targeted PR against correct branch (see CONTRIBUTING.md)

• [ ] Linked to github-issue with discussion and accepted design OR link to spec that describes this work.

• [ ] Wrote tests

• [ ] Updated relevant documentation (docs/)

• [ ] Added a relevant changelog entry to the Unreleased section in CHANGELOG.md

• [ ] Reviewed Files changed in the github PR explorer

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For Admin Use:

• Added appropriate labels to PR (ex. wip, ready-for-review, docs)
• Reviewers Assigned
• Squashed all commits, uses message "Merge PR #XYZ: [title]" (coding standards)

[codecov-commenter]

Codecov Report

Merging #3144 (7311a98) into dev (63f8bbd) will decrease coverage by 0.01%. The diff coverage is 20.00%.

:exclamation: Current head 7311a98 differs from pull request most recent head 4c769c9. Consider uploading reports for the commit 4c769c9 to get more accurate results

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@@            Coverage Diff             @@
##              dev    #3144      +/-   ##
==========================================
- Coverage   36.59%   36.58%   -0.01%     
==========================================
  Files         442      442              
  Lines       46414    46428      +14     
==========================================
+ Hits        16985    16988       +3     
- Misses      28169    28179      +10     
- Partials     1260     1261       +1     

Impacted Files	Coverage Δ
app/config/config.go	26.63% <20.00%> (-0.12%)	:arrow_down: