Add 413 HTTP error - CONTENT_TOO_LARGE

[hamorillo]

Closes #352

Description

This PR aims to solve the same issue as https://github.com/Automattic/Gravatar-SDK-iOS/pull/467 in the iOS repo.

When an image that is too big is uploaded, the server will answer with a 413, which we should handle and show the proper error message. For that reason, we need to add a new ErrorType.

Note: We've discussed ErrorType being a sealed class and the problems that could arise when adding a new ErrorType (Breaking change—it can break the compilation in a when clause). I'll open a different PR for that. #401

Testing Steps

As we are compressing and limiting the maximum size of the final image, it's not easy to test the changes. You have two options:

Modifying the code

• Apply the following patch (or comment the compression/size options in UCropCropperLauncher) Gravatar-Android-12-47-55.patch
• Build the demo-app
• Upload a huge image (you can use the resources from the iOS PR)

Mock the server response

• Using your favorite network tool (ex: Charles...) mock the response from the server when uploading an avatar - 413

In both options -> Verify you see the error on the avatar picker with the associated message.

[wpmobilebot]

📲 You can test the changes from this Pull Request in Gravatar Demo by scanning the QR code below to install the corresponding build.

	App Name	Gravatar Demo
	Commit	1fa495556f79d38e6dbc6a2e7b927980ea5b3efc
	Direct Download	gravatar-demo-prototype-build-pr402-1fa4955.apk