Add shared gRPC proto contract for portfolio items

[Copilot]

This spike explores defining the service interface in ironoc while leaving implementation to a separate module or repository. It introduces a contract-only protobuf definition for the existing portfolio-items use case so downstream services can generate shared types and implement the interface independently.

• What changed

  • Added src/main/proto/ironoc/portfolio/v1/portfolio_items.proto
  • Defined a PortfolioItemsService gRPC surface with a ListPortfolioItems RPC
  • Modeled PortfolioItem to match the current portfolio item payload shape used by ironoc

• Contract shape

  • Request includes pagination hooks:
    • page_size
    • page_token
  • Response includes:
    • items
    • next_page_token

• Documentation

  • Updated README.md with the contract location, protoc generation example, and intended usage pattern for external modules/projects

• Intended use

  • ironoc remains the owner of the interface definition
  • another module/project can generate Java types from the proto
  • that separate module can implement the gRPC server/client without coupling new functionality to the main web app

service PortfolioItemsService {
  rpc ListPortfolioItems(ListPortfolioItemsRequest) returns (ListPortfolioItemsResponse);
}

message ListPortfolioItemsRequest {
  int32 page_size = 1;
  string page_token = 2;
}

message ListPortfolioItemsResponse {
  repeated PortfolioItem items = 1;
  string next_page_token = 2;
}

[Copilot]

Pull request overview

Adds a contract-only gRPC/protobuf spike for portfolio project data so external modules can generate shared types and later implement the catalog service.

Changes:

• Added a new portfolio_projects.proto contract with a PortfolioProjectCatalog service and portfolio item messages.
• Documented how external projects can generate Java code from the shared proto contract.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
src/main/proto/ironoc/portfolio/v1/portfolio_projects.proto	Defines the initial portfolio gRPC/protobuf contract.
README.md	Adds documentation for locating and generating code from the proto spike.

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