fix: enforce path params are required

[iwong-isp]

Huma marks path params as required when generating the OpenAPI docs, which complies with OpenAPI 3.0. However, Huma does not check if path params values are non-empty during runtime.

For example, in the bookstore example, not providing the genre-id will result in a 404 after failing to find an empty genre instead of a 400.

restish :8888/v1/genres//books
HTTP/1.1 404 Not Found

{
  $schema: "https://localhost:8888/schemas/ErrorModel.json"
  detail: "Genre  not found"
  status: 404
  title: "Not Found"
}

Huma uses the Chi router which does not mark path parameters as required unless regex or additional custom logic is added. This PR modifies the resolver to check if a path param value is empty and throws an error instead of continuing.

The new output for the same bookstore request is as follows:

restish :8888/v1/genres//books
HTTP/1.1 400 Bad Request

{
  $schema: "https://localhost:8888/schemas/ErrorModel.json"
  detail: "Error while processing input parameters"
  errors: [
    {
      location: "path.genre-id"
      message: "genre-id is required"
      value: ""
    }
  ]
  status: 400
  title: "Bad Request"
}