feat(websockets): include exception cause to associate error with req

[kamilmysliwiec]

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: N/A

What is the new behavior?

Includes the cause attribute when emitting the exception message. This allows the error to be associated with the request that caused the exception.

Does this PR introduce a breaking change?

• Yes
• No

Other information

[coveralls]

Pull Request Test Coverage Report for Build 67accd4b-d6fe-4768-bd81-f529b1cf3559

Details

• 19 of 19 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.03%) to 90.138%

---

Totals
Change from base Build 0437aad1-7980-44fc-9973-959c535010f9:	0.03%
Covered Lines:	6983
Relevant Lines:	7747

---

💛 - Coveralls