How will we communicate SLSA generation failures to the end user?

Problem to solve

Errors might occur when the Rails backend generates a SLSA provenance statement, or when it uploads it as a job artifact. At the moment these errors are not surfaced in the GitLab UI, and users might not be aware that the provenance couldn't be generated or uploaded.

Example failures in generation could be:

• Provenance generation is not properly configured (config validation errors).
• Build does not have the required attributes.
• Provenance statement generation has been enqueued but build has since been deleted
• Environmental factors (such as lack of hard drive spice, etc.)

Proposal

Show SLSA provenance generation and upload failures in the UI using the approach detailed in #562795[Screenshot_2025-08-20_at_3.05.26_PM.png]