As a software engineer
I want to add a gRPC endpoint for private scratchpads
So that private scratchpad scan be created using third party gRPC clients

Given private_scratchpad_controller.rs and scratchpad_service.rs exist
When adding private_scratchpad_handler.rs
Then it should reflect private_scratchpad_controller.rs
And be added to a new &#39;grpc&#39; module under the root as grpc/private_scratchpad_handler.rs

Given gRPC requires protobuffer definitions
When adding private scratchpad gRPC endpoints
Then create gRPC service definition for private scratchpad request/response messages in /proto/private_scratchpad.proto

Given gRPC needs to be integrated with Tonic server
When adding private scratchpad gRPC endpoins
Then update lib.rs to integrate the gRPC private_scratchpad_handler.rs

Given there is a gRPC handler for pointers in /grpc/pointer_handler.rs
When adding the private_scratchpad_handler.rs
Then use private_scratchpad_handler.rs as an example

Provide unit tests where applicable to grpc/private_scratchpad_handler.rs and related new code.

Implementation Notes

- Assume other handlers will be added in the future, following the same pattern, in /grpc directory/module
- Define From traits to perform mapping between structs, including errors (use ?)
- Use Actix Data instead of Arc
- Place any unit tests at the bottom of the same file as the associated production code
- Increment patch version of anttp package in Cargo.toml