Show when credentials are misconfigured (basic UI)

On the Credentials settings page, it would be great to inform users of any credentials that are misconfigured

We should show an error icon or something next to the name when there's an issue.

A credential is misconfigured when:

• It has no values
• All required values are set
• It does not provide an env it needs to (this is something like: look at all the projects with access, get a list of all the envs across those projects, and ensure the credential provides a value for each env
• If it's oauth and expired maybe?

The envs thing is the big one - this is a quite a big issue in sandboxes right now.

This isn't the best place to show this information. We should probably add indicators to Workflow tables and the Workflow Diagram when a credential is misconfigured.

But this feels like the easiest place to start? We can add the logic to health check a credential, dump it in the settings page (which is useful if not intuitive), and then work it into nicer UX solutions later.

Start at the Credentials settings page and trace how credentials, required values, project access, environments, and OAuth expiry are represented. Define the health-check result and display behavior for empty or incomplete credentials; done when misconfigured credentials are visibly indicated there and the listed cases are covered.