feat: refreshes the token and reconnects if publishing fails

[jajeffries]

This pull request introduces a robust mechanism for proactively monitoring and refreshing JWT tokens used for Fleet MQTT connections. The changes add new configuration options, enhance token management, and implement background monitoring to ensure connections are refreshed before token expiry, reducing downtime and improving reliability.

Token expiry monitoring and proactive reconnection:

• Added a background goroutine in fleetConfigManager to periodically check JWT token expiry and trigger reconnection before the token expires, using new configuration options for check interval and buffer (monitorTokenExpiry, TokenExpiryCheckInterval, TokenReconnectBuffer). [1] [2]
• Implemented a channel-based mechanism (reconnectChan) and supporting logic to handle reconnection requests triggered by token expiry or imminent expiry. [1] [2]

Enhanced token management:

• Extended AuthTokenManager to store credentials, refresh tokens using stored values, and accurately track token expiry using the JWT exp claim with a safety buffer. Added methods for refreshing tokens, checking expiry, and extracting expiry time from JWTs. [1] [2] [3]

Configuration and state improvements:

• Updated fleetConfigManager to persist connection state, configuration, and backend information for use during reconnection events.

Logging and diagnostics:

• Improved logging throughout the token request, refresh, and expiry monitoring processes to aid diagnostics and troubleshooting. [1] [2]

These changes collectively improve the agent's resilience to token expiry, reduce manual intervention, and provide better observability into token lifecycle events.

[github-actions]

Go test coverage

STATUS	ELAPSED	PACKAGE	COVER	PASS	FAIL	SKIP
🟢 PASS	1.03s	github.com/netboxlabs/orb-agent/agent	8.2%	1	0	0
🟢 PASS	1.10s	github.com/netboxlabs/orb-agent/agent/backend	33.3%	30	0	0
🟢 PASS	4.02s	github.com/netboxlabs/orb-agent/agent/backend/devicediscovery	67.1%	2	0	0
🟢 PASS	0.11s	github.com/netboxlabs/orb-agent/agent/backend/mocks	0.0%	0	0	0
🟢 PASS	4.02s	github.com/netboxlabs/orb-agent/agent/backend/networkdiscovery	59.0%	2	0	0
🟢 PASS	4.02s	github.com/netboxlabs/orb-agent/agent/backend/opentelemetryinfinity	46.3%	2	0	0
🟢 PASS	4.03s	github.com/netboxlabs/orb-agent/agent/backend/pktvisor	67.0%	2	0	0
🟢 PASS	4.03s	github.com/netboxlabs/orb-agent/agent/backend/snmpdiscovery	58.5%	2	0	0
🟢 PASS	5.03s	github.com/netboxlabs/orb-agent/agent/backend/worker	68.1%	3	0	0
🟢 PASS	1.01s	github.com/netboxlabs/orb-agent/agent/config	100.0%	6	0	0
🟢 PASS	31.41s	github.com/netboxlabs/orb-agent/agent/configmgr	47.8%	26	0	0
🟢 PASS	7.61s	github.com/netboxlabs/orb-agent/agent/configmgr/fleet	66.0%	136	0	0
🟢 PASS	1.01s	github.com/netboxlabs/orb-agent/agent/otlpbridge	30.7%	5	0	0
🟢 PASS	1.01s	github.com/netboxlabs/orb-agent/agent/policies	100.0%	15	0	0
🟢 PASS	1.02s	github.com/netboxlabs/orb-agent/agent/policymgr	71.6%	11	0	0
🟢 PASS	25.66s	github.com/netboxlabs/orb-agent/agent/secretsmgr	48.9%	54	0	0
🟢 PASS	1.02s	github.com/netboxlabs/orb-agent/agent/telemetry	81.7%	19	0	0
🟢 PASS	1.01s	github.com/netboxlabs/orb-agent/agent/version	100.0%	1	0	0

Total coverage: 55.7%