Inventory Service Integration Tests

Problem/Feature Description

A warehouse management system exposes an InventoryService gRPC service with two methods: CheckStock and ReserveItems. The team has written the service implementation but has no integration tests. They want a proper Spring-based integration test setup that:

1. Starts the real service implementation (not a mock)
2. Connects a real gRPC client stub to it without requiring a network port to be open
3. Also includes a second test class that verifies the service works on a randomly allocated OS port (to avoid port conflicts in CI), with the client connecting to whatever port the server picked

The team is not sure which testing approach to use. They want the tests to use Spring's test framework (not plain JUnit with manual channel setup), and they want to keep things simple — no Docker, no external processes.

Output Specification

Produce the following files:

• pom.xml — Maven project with Spring gRPC and test dependencies
• src/main/java/.../InventoryServiceImpl.java — minimal service implementation (stub logic is fine)
• src/main/proto/inventory.proto — proto definition for the service
• src/test/java/.../InventoryInProcessTest.java — integration test using in-process transport (no real network port)
• src/test/java/.../InventoryPortTest.java — integration test connecting to a dynamically assigned port
• src/test/resources/application-test.properties — any test-specific configuration needed

Provide a notes.md explaining why each testing approach was chosen and how the client connects in each case.