fix(gateway): surface external plugin-entity faults (list, detail, freeze-frame) via fault-scope ownership

[mfaferek93]

External protocol-plugin entities (e.g. a PLC over OPC UA) report faults to the fault_manager under their entity id, but the per-entity SOVD fault routes dropped them: an external app has no ROS FQN, so fault-scope resolution produced an empty ownership set and the scope filter rejected every fault the entity reported.

• Fault-scope: an external app with no ROS binding now contributes its own entity id to its scope set, so it is recognised as the owner of faults reported under that id. ROS-bound entities are unchanged; the change is confined to the empty-FQN external case in the fault-scope resolution.
• Per-entity detail: for a plugin entity that owns the fault, the detail route returns the fault_manager's environment-enriched record (including the freeze-frame), consistent with the non-plugin detail path, and falls back to the plugin's own fault provider for faults the fault_manager does not hold.
• The per-entity list now surfaces the entity's faults via the same fixed ownership.
• Scope-guard behaviour (cross-entity disclosure on GET, cross-entity clear on DELETE) is unchanged for bound entities and covered by regression tests.

Closes #502.

[Copilot]

Pull request overview

This PR fixes per-entity SOVD fault list/detail behavior for external protocol-plugin entities (no ROS binding / empty FQN) by ensuring fault-scope ownership includes the entity’s bare ID in the external-app case, and by ensuring plugin-entity fault detail prefers the fault_manager’s environment-enriched record (freeze-frame) when the entity owns the fault, with a fallback to the plugin’s provider when the fault_manager doesn’t have it. This addresses #502’s root cause and acceptance criteria around list, detail, freeze-frame, and unchanged cross-entity guard behavior.

Changes:

• Extend fault-scope resolution so external Apps with empty effective_fqn() contribute their own entity ID as the owned scope token (non-external unbound apps remain skipped).
• Update fault detail handling for plugin-owned entities to prefer fault_manager’s get_fault_with_env payload when the fault is in the entity’s resolved scope, otherwise fall back to the plugin provider.
• Align OPC UA plugin + test fakes with the PluginContext::list_entity_faults contract (bare array), and add regression tests for ownership and freeze-frame propagation.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/ros2_medkit_plugins/ros2_medkit_opcua/test/test_opcua_plugin.cpp	Adjust test fake to return bare fault array; add regression test ensuring get_fault locates items in that array.
src/ros2_medkit_plugins/ros2_medkit_opcua/test/test_opcua_identity.cpp	Align identity test fake with bare-array list_entity_faults contract.
src/ros2_medkit_plugins/ros2_medkit_opcua/src/opcua_plugin.cpp	Consume list_entity_faults as a bare array for list/detail fault lookups.
src/ros2_medkit_gateway/test/test_plugin_entity_routing.cpp	Add test pinning plugin-fallback payload behavior when fault_manager does not hold the fault.
src/ros2_medkit_gateway/test/test_handler_context.cpp	Add tests proving external-app bare-ID ownership is granted only for external=true, and that bound-app behavior is unchanged.
src/ros2_medkit_gateway/test/test_fault_manager_routing.cpp	Add test pinning freeze-frame presence in fault_manager enriched detail payload for the external-entity case.
src/ros2_medkit_gateway/test/test_fault_handlers.cpp	Add tests for bare-ID scope matching/guard behavior and freeze-frame shaping in SOVD fault detail responses.
src/ros2_medkit_gateway/src/http/handlers/fault_handlers.cpp	Prefer fault_manager enriched detail for plugin entities when the fault is in-scope; otherwise fall back to plugin provider.
src/ros2_medkit_gateway/src/core/faults/fault_scope.cpp	Extend scope resolution: external app with empty FQN owns faults under its bare entity ID; non-external unbound app remains skipped.

[bburda]

Additional notes outside the inline comment:

• The get_fault enriched-vs-fallback branch (the main change) has no end-to-end handler test. The four pieces are unit-tested, but nothing builds a node and calls get_fault, so the security selection is unpinned: an entity that does NOT own a fault code must fall through to the plugin provider (404), not return another entity's enriched freeze-frame record. If the new scope check is later changed, a cross-entity read leak would not be caught.
• The per-entity list and single-fault clear routes for an external entity are only covered at the resolver unit level, not end to end. The empty-list bug this PR fixes has no regression test on its own route.

[bburda]

This says cross-entity clear (DELETE) flows through this predicate, but for a plugin or external entity it does not. The single-fault DELETE takes the is_plugin branch and delegates to the plugin clear_fault, which for OPC UA forwards the code to /fault_manager/clear_fault with no scope check. So DELETE /apps/A/faults/{code owned by B} clears B's fault. Either apply the same fault_in_source_scope guard on the plugin DELETE branch, or correct this comment so it does not claim a property the plugin path does not enforce.