Investigate CI failing for external contributors

[kyzooghost]

Description

Currently the CI for linea-monorepo fails to run for PRs made by external contributors

This is because Github Actions will not pass secrets when the workflow is triggered from a forked repository. As this is a security design choice by Github and there are no apparent quick risk-free fixes here, we will need to consider alternative CI design and security tradeoffs.

Motivation

See description

Tasks

• Investigate methods to enable CI to pass for external contributors

Acceptance criteria

• Design document +/- discussion

Risks

• Security risks introduced by any methods we are proposing

Remember to

• Add the documentation label in case there is an impact on the documentation
• Add priority and team labels
• Add Task for updating the Runbook or adding/updating existing metrics and alerts.