Require boolean value for 'use_iam_profile' in 'gitlab_rails["object_store_connection"]' section

Summary

The new use_iam_profile option in the consolidated gitlab_rails["object_store_connection"] does not warn if the strings 'true' or 'false' are used, instead of boolean true and false.

Using a string for this value will lead to workhorse failing to parse the S3config, resulting in error preAuthorizeHandler: decode authorization response: json: cannot unmarshal string into Go struct field S3Config.RemoteObject.ObjectStorage.S3Config.UseIamProfile of type bool

Proposal

Validate the value entered for use_iam_profile is a boolean.

References

ZenDesk ticket # 169153 (internal link)