Ensure callable functions have invoker correctly set to "public"

[chrisbrown-io]

Description

Implemented fix for issue introduced in v10.3.0 where callable functions were not having their invoker property correctly set to "public" that would in turn cause access issues with the deployed functions (as detailed in #4327).

Will also fix issues such as #3965, that are presumably cause by version mismatches/upgrades introducing this issue.

See comment for explicit info.

Fixes issue by adding specific handling for callable functions and always setting the invoker to "public".

Also fixed issue with taskQueueTrigger endpoints calling wrong method/passing wrong args when trying to set invoker.

Scenarios Tested

Thanks to @taeold we have explicit tests for each function type and the expected outcomes for both createV1Function and createV2Function methods.

Sample Commands

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

For more information, open the CLA check for this pull request.

[chrisbrown-io]

@taeold - you mentioned in your previous comment that the invoker is not updated on update, however the source code/tests for the update methods look as if they would update the invoker if set (and subsequently not update the invoker for callable functions unless additional logic was added).

Are you saying we don't need to handle this case, as users can't specify an invoker for callable functions, meaning this scenario of changing the invoker on update will never happen?

[taeold]

Are you saying we don't need to handle this case, as users can't specify an invoker for callable functions, meaning this scenario of changing the invoker on update will never happen?

Yes. User may have changed invoker for good reasons. I think we should respect that.

Also - can we add an entry to CHANGELOG.md file?

[taeold]

🔥 Amazing contribution!