Add strictPopulate type to PopulateOptions

[Kaljuk]

Added strictPopulate to PopulateOptions, otherwise given option can't be used in TS projects when enforcing types.

Summary

When using populate in mongoose 6, the types for populate options might've been overlooked. PopulateOptions interface is missing strictPopulate prop, so I added one, with description from the doc. Otherwise I can't use populate with given option.

Examples

await DocumentModel.findById('some_id')
  .populate({
    match: { somePath: { $ne: undefined } } 
    path: 'somePath',
    strictPopulate: false
  })

Previously this was not allowed in typescript dev environment due to enforcing of types, and a type error was thrown.
Now I added the respective type and all works.

For future reference
It seems that the options?: any seems to be unnecessary and wrongfully referring to options.options. But when we look at the current codebase with strictPopulate for example, then the value will be taken from options.strictPopulate, not options.options.strictPopulate.

TL;DR I'd suggest removing the options?: any from the PopulateOptions entirely and replace it with the specific options (i.e. strictPopulate, like in this PR)

[AbdelrahmanHafez]

Welcome, @Kaljuk 👋

Other than the missing test, LGTM.
I agree that having typed options is better than any, and I personally think that having them all in one place would be more accurate, either top-level or all in options.

Sadly we can't do that change now because it'll be backward breaking, we should at least add accurate typings to represent the API.

You're more than welcome to submit PRs improving the types.

[vkarpov15]

Thanks 👍