Ego Application Credential Auth on Request

[joneubank]

Provide a configurable way for the job to authenticate vs Ego then provide an application scoped JWT to the request. This would allow interaction with services that have restricted end points.

To accomplish this we need to connect the job to Vault to grab application client-secret, so this feature involves 3 pieces:

1. Call to Vault to get application credentials.
2. Call to Ego to get JWT
3. Add the JWT as a Authorization header on the request.

Configuration needed for this would be the client ID/Secret, OR the vault connection details to fetch these properties.