feat(microservices): Add oauth bearer to SASLOptions

[smhmayboudi]

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
[X] 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: #5635

What is the new behavior?

  sasl: {
    mechanism: 'oauthbearer',
    oauthBearerProvider: async () => {
      // Use an unsecured token...
      const token = jwt.sign({ sub: 'test' }, 'abc', { algorithm: 'none' })

      // ...or, more realistically, grab the token from some OAuth endpoint

      return {
        value: token
      }
    }
  },

Does this PR introduce a breaking change?

[ ] Yes
[X] No

Other information

[coveralls]

Pull Request Test Coverage Report for Build 31683

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 160 unchanged lines in 31 files lost coverage.
• Overall coverage increased (+0.7%) to 95.443%

---

Files with Coverage Reduction	New Missed Lines	%
packages/common/decorators/http/route-params.decorator.ts	1	88.1%
packages/common/pipes/validation.pipe.ts	1	94.38%
packages/core/router/router-execution-context.ts	1	97.42%
packages/microservices/client/client-redis.ts	1	92.86%
packages/microservices/server/server-kafka.ts	1	97.54%
packages/microservices/server/server-mqtt.ts	1	96.83%
packages/websockets/socket-server-provider.ts	1	91.18%
packages/common/decorators/core/apply-decorators.ts	2	66.67%
packages/common/decorators/core/set-metadata.decorator.ts	2	85.71%
packages/microservices/client/client-kafka.ts	2	97.12%

Totals
Change from base Build 31dcaa7c-d83e-4300-bead-bda09e984628:	0.7%
Covered Lines:	4482
Relevant Lines:	4696

---

💛 - Coveralls

[galesky]

Hello @smhmayboudi

Given that implementing oauthbearer makes the username and password optional on the SASLOptions interface, what are your thoughts on refining the Interface a little so that those properties are not ALWAYS optional ?

I'm coming from the idea that for the other 5 "SASLMechism"s the username and password are still required.

edit: typo

[kamilmysliwiec]

Ping @smhmayboudi 🏓