Feature request: Add support to mock generator for non required fields

[petkostas]

I am using libopenapi in a project to render documentation, and I used the mock generator to render the responses of different operations.
While it was working as expected, I encountered a minor annoyance. I crossed a case where the Media type response had no example and used a schema reference.
The mock generator generated a mock response, but I noticed it was omitting a few fields. After a couple of experiments, I realized that this behavior was related to the use of required in the schema object. Removing this provided a complete working example.
Is there a way to switch this (maybe through an mg.OnlyRequired() switch? That would greatly help, especially when you prefer to render a complete response example for schemas that include a required field.
Let me know if I can help. I can open a PR for this.

P.S. Heh #200 nice 👍🏼 😄

[daveshanley]

1. Would you expect this to be a different method, or a configuration?
2. Would you expect the 'switch' (however its implemented) to render all fields, regardless of 'required' state?

[petkostas]

Hello @daveshanley, a different method would be sufficient for me (and also keeps things clean). The expected behavior would be that when calling that method, you get a mock with all the schema fields regardless of the required state.

[daveshanley]

Added in v0.13.12

A new switch method features on the renderer.SchemaRenderer struct called DisableRequiredCheck() This will render all properties, regardless of the 'required` property values.