Make custom property on options optional

[zbarbuto]

For instances where you have a custom controller that implements CrudController<T> with a custom endpoint that wants to use TypeOrmCrudService<T> it's nice to just be able to, for example, call

await this.service.getMany({
 options: { query: { limit: 10 } }
})

Without being required to pass in operators. At the moment the above would error with can not read property 'custom' of undefined

[coveralls]

Pull Request Test Coverage Report for Build 2580929203

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 4 of 4 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.2%) to 99.782%

---

Totals
Change from base Build 2575515495:	-0.2%
Covered Lines:	1194
Relevant Lines:	1194

---

💛 - Coveralls

[zaro]

@zbarbuto Thank you, I think the change makes sense.