fix(fastify): uppercase http method names

[rickdgeerling]

Fastify expects uppercase and won't auto-add the HEAD method otherwise

Closes #13016

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

What is the current behavior?

When a GET endpoint is registered with Fastify, Nest responds with 404 on a HEAD request

Issue Number: #14016

What is the new behavior?

Fastify correctly detects that the endpoint is a GET and auto-adds a HEAD handler too.

Does this PR introduce a breaking change?

• Yes
• No

Other information

The Fastify logic is here and you can see it expects uppercase method names:
https://github.com/fastify/fastify/blob/238d8a4f78b75c88e7b69b2d97fe27dd93fc520d/lib/route.js#L210

[coveralls]

Pull Request Test Coverage Report for Build 8b73c825-d0d8-4cef-b907-65fac944bd49

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 92.213%

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Totals
Change from base Build 72800da6-9207-4c7a-b092-bed81bb676c8:	0.0%
Covered Lines:	6750
Relevant Lines:	7320

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💛 - Coveralls

[micalevisk]

@tuxmachine could you please add a comment anywhere in that file to clarify that we must use the uppercased in there?

Ideally, integration tests should prevent this