feat: move to hard coded topics and move agent id into config

[jajeffries]

This pull request refactors how the agent's ID and MQTT topics are managed and used throughout the fleet manager and heartbeater components. The changes remove legacy topic configuration fields, introduce a dedicated agent_id field, and update how topics are generated and passed between components. Unit tests are updated to reflect these changes and ensure correct agent ID handling in heartbeat messages.

Configuration and Topic Management Updates:

• Removed legacy topic configuration fields (HeartbeatTopic, CapabilitiesTopic, TopicName) from the FleetManager struct and added a new AgentID field for explicit agent identification. (agent/config/types.go)
• Refactored topic generation: now topics are derived using a new template function based on JWT claims and the configured agent_id, instead of merging configuration and token response values. (agent/configmgr/fleet.go)

Heartbeater and Fleet Manager Refactoring:

• Updated sendSingleHeartbeat and sendHeartbeats methods to accept and use the agentID parameter, ensuring heartbeats carry the correct agent identity. (agent/configmgr/fleet.go) [1] [2]
• Changed fleet manager connection logic to propagate agentID through all relevant calls, including MQTT connection setup. (agent/configmgr/fleet.go) [1] [2] [3]

Token Response Structure Changes:

• Removed the Topics field from the tokenResponse struct, as topic information is now generated separately from JWT and configuration. (agent/configmgr/fleet.go)

Unit Test Updates:

• Updated all heartbeater and fleet manager tests to pass and assert the correct agent_id value, and removed references to legacy topic fields and token response topics. (agent/configmgr/fleet_test.go) [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19]

[github-actions]

Go test coverage

STATUS	ELAPSED	PACKAGE	COVER	PASS	FAIL	SKIP
🟢 PASS	0.01s	github.com/netboxlabs/orb-agent/agent	0.0%	0	0	0
🟢 PASS	0.01s	github.com/netboxlabs/orb-agent/agent/backend	0.0%	0	0	0
🟢 PASS	5.03s	github.com/netboxlabs/orb-agent/agent/backend/devicediscovery	76.0%	3	0	0
🟢 PASS	0.00s	github.com/netboxlabs/orb-agent/agent/backend/mocks	0.0%	0	0	0
🟢 PASS	5.03s	github.com/netboxlabs/orb-agent/agent/backend/networkdiscovery	75.8%	3	0	0
🟢 PASS	4.02s	github.com/netboxlabs/orb-agent/agent/backend/otel	76.4%	2	0	0
🟢 PASS	3.02s	github.com/netboxlabs/orb-agent/agent/backend/pktvisor	65.6%	2	0	0
🟢 PASS	5.03s	github.com/netboxlabs/orb-agent/agent/backend/snmpdiscovery	75.8%	3	0	0
🟢 PASS	5.03s	github.com/netboxlabs/orb-agent/agent/backend/worker	76.0%	3	0	0
🟢 PASS	1.01s	github.com/netboxlabs/orb-agent/agent/config	100.0%	6	0	0
🟢 PASS	61.49s	github.com/netboxlabs/orb-agent/agent/configmgr	59.8%	66	0	0
🟢 PASS	1.01s	github.com/netboxlabs/orb-agent/agent/policies	100.0%	15	0	0
🟢 PASS	1.03s	github.com/netboxlabs/orb-agent/agent/policymgr	70.3%	10	0	0
🟢 PASS	24.57s	github.com/netboxlabs/orb-agent/agent/secretsmgr	45.7%	45	0	0
🟢 PASS	1.01s	github.com/netboxlabs/orb-agent/agent/version	100.0%	1	0	0

Total coverage: 59.9%

[leoparente]

LGTM