Carried over from #154

Is your feature request related to a problem?

Currently there is no support for handling discriminators. Moreover, discriminator $ref pointers don't adhere to JSON Schema specification and are thus not resolved by our parser/resolver. This means we will need to resolve discriminator $ref pointers on-demand.

Describe the solution you'd like

• Implement support for discriminators.
• Render schema mappings at the same level as the property we're applying the discriminator to (may necessitate a new UI component or setting the marginLeft to "-2.4rem")
• Leverage the OpenAPIParser class byRef() method to resolve $ref pointers. (Will require instantiating and passing a parser instance for each spec we read in)

Describe alternatives you've considered

Explored using oneOf in place of discriminator but it renders the schema as a child of the property which does not satisfy the requirements.

Additional context

ReDocly has a group write up on this and their ReDoc demo demonstrates the correct implementation: https://redocly.com/docs/resources/discriminator/