feat: secrets manager interface

[leoparente]

This pull request introduces a new secrets management system to the orb-agent by integrating a secretsmgr package and updating relevant parts of the codebase to support it. The most important changes include adding a new secrets manager, updating the configuration structures, and modifying the ConfigManager to handle secrets.

Integration of Secrets Management:

• agent/agent.go: Added secretsmgr.Manager to the orbAgent struct and initialized it in the New function. The secretsManager is now started in the Start method. [1] [2] [3] [4]
• agent/config/types.go: Introduced new configuration types VaultManager, SecretsSources, and ManagerSecrets to support secrets management. Updated OrbAgent struct to include ManagerSecrets. [1] [2]

Modifications to Config Manager:

• agent/configmgr/manager.go: Updated the New function to accept a secretsmgr.Manager and pass it to the localConfigManager and gitConfigManager. [1] [2]
• agent/configmgr/git.go and agent/configmgr/local.go: Added secretsmgr.Manager to the configuration managers and modified the applyPolicies method to use SolveSecrets for processing secrets. [1] [2] [3] [4]

New Secrets Manager Implementation:

• agent/secretsmgr/manager.go: Introduced the secretsmgr package with an interface for managing secrets and a factory method for creating instances based on configuration.
• agent/secretsmgr/vault.go: Implemented vaultManager for managing secrets using HashiCorp Vault, including methods for starting the manager, registering update callbacks, and solving secrets.
• agent/secretsmgr/vault_auth.go: Added various authentication methods for Vault, including token, AppRole, userpass, Kubernetes, and LDAP.

Dependency Updates:

• go.mod: Added the github.com/hashicorp/vault/api dependency to support Vault integration.

[github-actions]

Go test coverage

STATUS	ELAPSED	PACKAGE	COVER	PASS	FAIL	SKIP
🟢 PASS	1.02s	github.com/netboxlabs/orb-agent/agent	0.0%	1	0	0
🟢 PASS	0.15s	github.com/netboxlabs/orb-agent/agent/backend	0.0%	0	0	0
🟢 PASS	0.00s	github.com/netboxlabs/orb-agent/agent/backend/devicediscovery	0.0%	0	0	0
🟢 PASS	0.01s	github.com/netboxlabs/orb-agent/agent/backend/networkdiscovery	0.0%	0	0	0
🟢 PASS	0.00s	github.com/netboxlabs/orb-agent/agent/backend/otel	0.0%	0	0	0
🟢 PASS	0.00s	github.com/netboxlabs/orb-agent/agent/backend/pktvisor	0.0%	0	0	0
🟢 PASS	0.00s	github.com/netboxlabs/orb-agent/agent/backend/worker	0.0%	0	0	0
🟢 PASS	0.00s	github.com/netboxlabs/orb-agent/agent/configmgr	0.0%	0	0	0
🟢 PASS	0.00s	github.com/netboxlabs/orb-agent/agent/policies	0.0%	0	0	0
🟢 PASS	0.00s	github.com/netboxlabs/orb-agent/agent/policymgr	0.0%	0	0	0
🟢 PASS	1.73s	github.com/netboxlabs/orb-agent/agent/secretsmgr	8.0%	7	0	0
🟢 PASS	1.01s	github.com/netboxlabs/orb-agent/agent/version	100.0%	1	0	0

Total coverage: 1.7%

[mfiedorowicz]

LGTM, one ask though