feat: add @ApiWebhook() for OAS 3.1 or later

[undownding]

PR Checklist

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• 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: #1827

What is the new behavior?

Add a new decorator @ApiWebhook() for OAS 3.1 and later.

  @Controller()
  class StripeWebhooksController {
    @Post('stripe')
    @ApiWebhook('stripeEvent')
    stripe() {
      return { ok: true };
    }
  }

If document.openapi is set to default or 3.0.0, @ApiWebhook() will maintain the same output as before.

If document.openapi is set to 3.1.0 or later, the API will remove from document.paths and add to document.webhooks

Does this PR introduce a breaking change?

• Yes
• No

Other information

[kamilmysliwiec]

Could you resolve conflicts?