feat(fastify-adapter): support for skipping middie registration

[ancyrweb]

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?

Issue Number: 13729

What is the new behavior?

It's possible to skip middie registration by passing a skipMiddie flag.

Does this PR introduce a breaking change?

• Yes
• No

Other information

[coveralls]

Pull Request Test Coverage Report for Build 595ba74a-45b7-4bee-90c3-f108e75e965c

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.001%) to 92.207%

---

Files with Coverage Reduction	New Missed Lines	%
packages/core/scanner.ts	2	88.46%

Totals
Change from base Build 7d588bd4-21c3-461c-a6f6-d4bb4122dd2a:	-0.001%
Covered Lines:	6744
Relevant Lines:	7314

---

💛 - Coveralls