Return correct HTTP code if context creation fails

[MrLoh]

Here's a proposal to fix #1709 in cases, where apollo already returns a 400 response, to handle the default AuthenticationError and ForbiddenError with fitting HTTP status codes. It doesn't make sense, that these errors set a status code, when thrown from a resolver, since partial data might still be returned in that case, but when the context creation fails, Apollo might as well return a more meaningful status code.

TODO:

• Update CHANGELOG.md with your change (include reference to issue & this PR)
• Make sure all of the significant new logic is covered by tests
• Rebase your changes on master so that they can be merged easily
• Make sure all tests and linter rules pass

[apollo-cla]

@MrLoh: Thank you for submitting a pull request! Before we can merge it, you'll need to sign the Meteor Contributor Agreement here: https://contribute.meteor.com/

[anilexpedia]

Any idea when this will be merged? I think this is useful functionality to expose through graphql.

[pragone]

Hey... This PR seems to have gone a bit stale, so I've resubmitted as #2269