docs: add @APIResponse annotations to config REST interfaces

[ginccc]

Summary

Several REST interfaces have @Operation annotations but are missing @APIResponse annotations for HTTP status codes. Adding these improves the generated OpenAPI spec and Swagger UI documentation.

Interfaces to update

Interface	Methods needing @APIResponse
configs/IRestVersionInfo.java	2
configs/properties/IRestPropertiesStore.java	3
configs/deployment/IRestDeploymentStore.java	1
configs/descriptors/IRestDocumentDescriptorStore.java	4
configs/channels/IRestChannelIntegrationStore.java	6
configs/agents/IRestCapabilityRegistry.java	2

Pattern to follow

See IRestAgentStore.java for the established pattern:

@GET
@APIResponse(responseCode = "200", description = "The agent configuration")
@APIResponse(responseCode = "404", description = "Agent not found")
@Operation(description = "Read agent.")
Response readAgent(...);

Common status codes by HTTP method:

• GET by ID → 200, 404
• GET list → 200
• POST create → 201, 400
• PUT update → 200, 400, 404
• DELETE → 204, 404

Check the implementation class when in doubt about which status codes are actually returned.

Acceptance criteria

• All listed methods have @APIResponse annotations
• Status codes match actual behavior
• ./mvnw compile passes

[Atharva759]

Hi @ginccc,

I would love to work on this issue! It looks like a great opportunity to get familiar with the codebase.

Could you please assign it to me? I'll follow the pattern from IRestAgentStore.java and make sure ./mvnw compile passes before opening a PR.