feat(matchedData): add generic types for return

[otorrillas]

Description

As brought up in #1041, it's currently hard to type the result of parsedData. It comes with all fields set as any unless we do a type assertion via the as keyword.

const { something } = parsedData(req);
// something has any type

const { something } = parsedData(req) as { something: string };
// something has string type

However, this syntax overrides all type-checking. To mitigate that, this PR adds an optional generic type to the parsedData function signature, so it becomes:

function matchedData<T = Record<string, any>>(
  req: Request,
  options: Partial<MatchedDataOptions> = {},
): T {
	// ...
}

Allowing users to keep using matchedData with the same signature as before:

const { something } = parsedData(req);
// something has any type

but to provide a type signature of the expected return (if it's been validated) if they'd like:

const { something } = parsedData<{ something: string }>(req);
// something has string type

There are no breaking changes, since matchedData still keeps Record<string, any> as the default return type.

Note

While types might not be strictly accurate depending on how the generic type is created, I believe it's better than the current solution (Record<string, any>).
As suggested in #1041 (comment), though, I believe a more type could be provided from the library depending on the options provided (e.g. with includeOptionals: true) via type guards. I'm open to exploring that direction further if you (maintainers) believe it might be worth implementing 👍

To-do list

• I have added tests for what I changed.

• This pull request is ready to merge.

[arafatkn]

Looking good.

[gustavohenke]

thanks, this is an excellent enhancement 😃

[gustavohenke]

Had to make a fix here; missed how _(...).reduce() automatically unwraps the result value, meaning that this valueOf() was incorrect here.