bugfix(@nestjs/passport) return correct type from PassportStragegy

[mleguen]

Type the return value of PassportStrategy() as a Strategy instead of a 'typeof Strategy'

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?

[x] 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?

import { Strategy } from 'passport-saml';
import { PassportStrategy } from '@nestjs/passport';

export class SamlStrategy extends PassportStrategy(Strategy) {
  // [...]
  generateServiceProviderMetadata(): string {
    // type error: super has type "typeof Strategy" which has no generateServiceProviderMetadata member
    return super.generateServiceProviderMetadata(...);
  }
}

What is the new behavior?

import { Strategy } from 'passport-saml';
import { PassportStrategy } from '@nestjs/passport';

export class SamlStrategy extends PassportStrategy(Strategy) {
  // [...]
  generateServiceProviderMetadata(): string {
    // OK: super has type "Strategy" which has a generateServiceProviderMetadata member
    return super.generateServiceProviderMetadata(...);
  }
}

Does this PR introduce a breaking change?

[ ] Yes
[X] No

Other information

[kamilmysliwiec]

Shouldn't we change this line:

Strategy: T,

instead?

[mleguen]

You mean Strategy: Type<T> and T extends any? That was my first try and it did not work.

[kamilmysliwiec]

Fixed here #134