Add process step status list to /api/issuer

[Phil91]

Description

To be able to retrigger a failed process step of the credential creation process a list of process steps and their status should be returned from the api /api/issuer

Acceptance Criteria

• An object with two properties processId and processSteps should be returned, the processSteps property should be a list of process steps with their type and their status and should be returned for the endpoint above.
• If no process exists for a credential the new property should be null
• UnitTests are added

Additional Information

Needed for eclipse-tractusx/portal-frontend#1340