2021.6

#133, improved error reporting

Sometimes parsing errors of the OpenAPI description were not be properly reported (e.g. by the maven plugin). Parsing/validation errors are now handled and reported at the processor level and reporting no longer depends on the plugin that calls the processor (gradle/maven).

#134, nested oneOf & anyOf

if an oneOf/anyOf was used in a schema property the processor generated code that used a non-existing class as java type for the property.

dependency updates

• updated openapi-processor-core to 2021.6 (was 2021.5)
• updated swagger parser to 2.0.28 (was 2.0.27)