NewGRPCUserServer makes user service available as a gRPC UserServer.

NewHTTPHandler attaches service API endpoints to HTTP routes in REST-style fashion.

NewLoggingMiddleware makes a logging middleware for UserService that logs user creation attempts, and which errors occurred (invalid username format, storage connection errors).

NewService configures new UserService that manages user accounts.

WithLogger configures a logger to debug the service.

CreateUserReq collects the request parameters for the CreateUser method.

CreateUserResp collects the response values for the CreateUser method.

FindUserByIDReq collects the request parameters for the FindUserByID method.

FindUserByIDResp collects the response values for the FindUserByID method.

ConfigOption configures the UserService.