Docs: document steps to publish layers in a new region

[dreamorosi]

What were you searching in the docs?

Currently when adding a new commercial region to the Lambda Layers we rely on an undocumented process which has proven to be error prone.

We should have these steps documented in the maintainers' handbook.

Is this related to an existing documentation section?

https://docs.powertools.aws.dev/lambda/typescript/latest/maintainers/#maintainer-responsibilities

How can we improve?

We should add a dedicated section to the maintainers handbook that details the steps needed to publish layers in a new region for the first time.

This can be in the form of a checklist or a paragraph, but it should cover all the actions needed before making a release that involve a new region where Lambda Layer is published.

Got a suggestion in mind?

On the top of my head the steps should be:

• bootstrap the new region both in the layers beta & prod accounts (this includes opting in + running CDK bootstrap)
• align the layer version to the latest so that the next release yields the same version number across regions (ideally include the script used either in the repo or the GH organization if shared with Python)
• add the region to the list in the workflow
• add the ARN in the docs

I might be missing some steps so please feel free to complement

Acknowledgment

• I understand the final update might be different from my proposed suggestion, or refused.

[dreamorosi]

I'm going to take the issue and open a PR shortly.