feat(repository): add findByForeignKeys function

[nabdelgadir]

Implemented initial version of the new helper function findByForeignKeys.

Resolves #3443.

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• npm test passes on your machine
• New tests added or existing tests modified to cover all changes
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• API Documentation in code was updated
• Documentation in /docs/site was updated
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[raymondfeng]

Can we accept a single value too? For example:

fkValues: ForeignKey[] | ForeignKey,

[raymondfeng]

Is it possible to have a type param such as FK extends StringKeyOf<Target> and use it to constrain fk values, such as Target[FK]?

[agnes512]

Let me reword it to make sure that I understand the type constrains in tsc correctly:

if we do foreignKey extends StringKeyOf<Target>, it would constrain the passed in foreignKey to be a string-like <Target> instance?

[raymondfeng]

I'm proposing the following:

export async function findByForeignKeys<
  Target extends Entity,
  FK extends StringKeyOf<Target>,
  TargetRelations extends object,
>(
  targetRepository: EntityCrudRepository<Target, unknown, TargetRelations>,
  fkName: FK,
  fkValues: Target[FK][],
  scope?: Filter<Target>,
  options?: Options,
): Promise<(Target & TargetRelations)[]> {
}

[raymondfeng]

Let's add a shortcut for empty array to return [] immediately. Include a test to cover this corner case too.

[nabdelgadir]

If we pass in an empty array, it complains that Type 'never[]' is not assignable to type 'number'. (or whatever the type of the foreign key value is)

[raymondfeng]

You can do the following:

const fkIds: number[] = []; 

[raymondfeng]

Maybe it's not necessary to export this type?