Better response error handling

[F0x1d]

Hi there. This pull request is about #17 and my comment there. I added PapyrusResponseError, which extends PapyrusError.

Now we can have something like this:

API:

@API
protocol GPT {
    @POST("images/generations")
    func generateImage(body: Body<GenerateImageRequestBody>) async throws -> GenerateImageResponse
}

Repository:

let body = ...
return try await gptApi.generateImage(body: body)

Some error handling, for example in ViewModel:

func handleError(_ error: Error) async {
    guard let error = error as? PapyrusError else { return }
    var message = error.message
    
    if let response = (error as? PapyrusResponseError)?.response,
       let responseError = try? response.decode(ErrorResponse.self, using: decoder) {
        message = responseError.error.message
    }
    
    self.error = message
}

I don't think this is the best solution for now. Waiting for you comments.

[F0x1d]

BTW, this way

... -> Response

methods will also throw PapyrusError. I think this is more intuitive. So, docs should be updated

[joshuawright11]

This is great @F0x1d ! I was thinking of doing things the same way.

How about we give an optional let request: Request? and let response: Response? to PapyrusError and we can use that error for everything (passing a request and response if one or both are available)?

[F0x1d]

I thought it would be strange to have the same error for something like Incorrect url and something like Unsuccessful status code, but, yeah, you are right, it makes life simpler

[joshuawright11]

Looks great 🎉