feat: errors for responses

[prestwich]

• Adds shortcut methods to instantiate response errors
• Adds serialize_payload to the response objects to allow easy converting to the default Response

This is a breaking change, as it changes the ErrorPayload message to a Cow. However, it doesn't break anything in the library/

Motivation

Solution

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes

[mattsse]

all of these seem fine, the Cow makes sense, though only really for server POV