fix: handling not exist gracefully

[israel]

This is my first PR here so I have made changes to only some of the resources. Once approved I will do the same for the rest. Thanks

Changed handling of not exists scenarios for read resource functions for User, API Integration and External Function resources

Test Plan

Updated user_test to reflect the change.

References

[sfc-gh-swinkler]

Hello @israel, thank you for your PR!

I think this is good, just I would ask for you to create a new file called errors.go at pkg/snowflake/errors.go to declare this error as a constant. For example, take a look at how this provider did the same thing you are doing:
https://github.com/hashicorp/terraform-provider-tfe/blob/main/tfe/resource_tfe_team.go#L155-L162

and then they declared that error in the errors.go file:
https://github.com/hashicorp/go-tfe/blob/main/errors.go#L13

This is not something we are currently doing, but its a pattern I would like to start abiding by. If you could please do this I would be much obliged.

[israel]

Hi @sfc-gh-swinkler
Apologies for the delayed response, I have not seen the notification for some reason...
I have moved the generic error from external_function.go to a common errors file as you requested.
Thanks,
Israel

[sfc-gh-swinkler]

/ok-to-test sha=7a8f66b

[github-actions]

Integration tests success for 7a8f66b

[sfc-gh-swinkler]

Thank you for your contribution! @israel