Extend Rails zoekt heartbeat API to accept services attribute

Problem

For each zoekt node we store a list of services supported by the node (currently only "zoekt" and "knowledge_graph" services are supported). We plan to start zoekt in "zoekt-orchestrator" mode - in this mode zoekt will act as a proxy to GKG services. If zoekt service runs in this zoekt-orchestrator mode, it will support processing knowledge graph tasks, otherwise it will support processing zoekt search tasks.

Proposal

Extend Rails' heartbeat API endpoint to accept services optional parameter and update zoekt node's record based on this value sent by zoekt nodes.