Conditionally creates billing sink if the billing account is of type resource

[Ali-Aburub]

Conditionally creates billing sink if the billing account is of type resource

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Checklist

I applicable, I acknowledge that I have:

• Read the contributing guide
• Ran terraform fmt on all modified files
• Regenerated the relevant README.md files using tools/tfdoc.py
• Made sure all relevant tests pass

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[ludoo]

Nice PR, left a couple minor comments then once checks pass it's good to go. Thanks :)

[ludoo]

One more comment: we should have a moved block to transition IAM from the resource to the module, if possible.

[Ali-Aburub]

One more comment: we should have a moved block to transition IAM from the resource to the module, if possible.

Currently the billing IAM assignments are additive. With the refactoring I did, I changed it to be authoritative since these roles will not be touched on later stages. Do you agree with this change? @ludoo

[ludoo]

One more comment: we should have a moved block to transition IAM from the resource to the module, if possible.

Currently the billing IAM assignments are additive. With the refactoring I did, I changed it to be authoritative since these roles will not be touched on later stages. Do you agree with this change? @ludoo

actually no, they should be additive as the assumption is an external billing account is not exclusively managed here

[ludoo]

IAM needs to be additive, unless we also add an option in the billing account variable to control this

[Ali-Aburub]

@ludoo Thank you Ludo for the guidance. I changed the IAM bindings to be additive, with processing logic implemented in the locals block. I also introduced a new option to the billing account variable which explicitly determines the creation of a log bucket, log sink, and IAM log writer assignment