Set up signed commits for github-ci-user

[dms1981]

User Story

As a Modernisation Platform engineer
I need to configure signed commits for our github-ci-user
So that when it creates pull requests they are signed in compliance with our branch protection policies

Value / Purpose

We require signed commits when pull requests are raised against our repositories. At present our github-ci-user does not have commit signing configured. By setting up commit signing we can avoid a situation where - for example - we create a new account, the CI user raises a pull request based on our template files, and we have to disable commit signing in order to merge it in.

Context / Background

We introduced required commit signing through this issue.

The hard part has been done - getting actions to sign their commits - but the CI user needs to have signed commits set up for PRs created through its use in GitHub actions as part of environment setups.

Useful Contacts

No response

Additional Information

No response

Definition of Done

• Set up commit signing for CI user
• Store details for commit signing if required in Modernisation Platform AWS Secrets Manager secret version that currently holds CI user creds
• Confirm that CI user submits signed commits