feat(shibboleth-plugin): TrustRelationship Activation API

New M2M API to reconcile a trust relationship's desired state against the actual IdP. Through it a worker announces liveness, claims a unit of work, renews its claim, and reports the outcome.

## Endpoint

| Method | Path | Operation |
|---|---|---|
| `POST` | `/workers` | Register / re-announce a worker (idempotent). |
| `POST` | `/workers/{worker}/heartbeat` | Renew a worker's liveness (`{worker}` = URL-encoded origin). |
| `POST` | `/work-items/claim-next` | Atomically claim the oldest available item of a type. |
| `GET` | `/work-items/{id}` | Read a work item. |
| `POST` | `/work-items/{id}/heartbeat` | Renew the lease on an assigned item. |
| `POST` | `/work-items/{id}/report` | Report an activation outcome. |

For more details refer [trust-activation-api.md](https://github.com/JanssenProject/jans/edit/issue_13590/jans-shibboleth-idp/docs/issues/trust-activation-api.md)