feat(jans-edarling): implement lock server integration

[rmarinn]

Is your feature request related to a problem? Please describe.

Cedarling needs to be able to integrate with the lock server as described in steps 10-20. In this diagram:

Describe the solution you'd like

The connection during the startup sequence can be implemented as follows:

1. Check if the CEDARLING_LOCK bootstrap property is set to "enabled"
2. Validate the CEDARLING_LOCK_SSA JWT.
3. Send a POST request to the IDP's /register endpoint
4. Recieve a 201 response together with a client_id
5. Get an access token via the /token endpoint
6. Get the policy store through the /config endpoint together with the access_token scoped to "cedarling".
7. POST to the /audit endpoint
8. Subscribe to the SSE through the /lock_sse
9. Listen to SSE

Describe alternatives you've considered

N/A

Additional context

Using the Lock server is optional and could be toggled using the CEDARLING_LOCK bootstrap property.