feat(websocket): request scoped gateways

[microwavekonijn]

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: #4287

What is the new behavior?

Added scope option to websocket gateway so a gateway resolves per connection.

Does this PR introduce a breaking change?

• Yes
• No

[kamilmysliwiec]

Thanks for your suggestion!

This has been discussed in the past and we decided to not implement it in the foreseeable future.

If you think your request could live outside Nest's scope, we'd encourage you to collaborate with the community on publishing it as an open source package.