fix(microservices): use switch case for types of statuses in server

[bittlerr]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

What is the current behavior?

The debug message of nats server appears even if debug mode is false, it seems that was fixed only on client side, not server one.
DEBUG [Server] NatsStatus: type: "pingTimer", data: "1".

Issue Number: 10783

What is the new behavior?

I filter out message if debug mode is false.

Does this PR introduce a breaking change?

• Yes
• No

Other information

[coveralls]

Pull Request Test Coverage Report for Build 742cca57-b5d5-4662-a650-264f5423af0b

• 5 of 8 (62.5%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.03%) to 92.959%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
packages/microservices/server/server-nats.ts	5	8	62.5%

Totals
Change from base Build a491a671-3dc9-4afe-b7e0-675925f5f9aa:	-0.03%
Covered Lines:	6377
Relevant Lines:	6860

---

💛 - Coveralls

[micalevisk]

so this is a fix rather than a refactor, right?

could you please retitle your PR (for changelog sake)

[kamilmysliwiec]

lgtm