Schemas using `allOf` and `required` do not generate properly in Java

Description

If you have a schema that uses allOf like so:

allOf:
  - $ref: '#/definitions/Base'
properties:
  uuidProp:
    type: string
    format: uuid
  stringProp:
    type: string
required:
  - uuidProp
  - stringProp

where Base

properties:
  baseProp:
    type: string
required: 
  - baseProp

The generated code only respects the required property on the base schema and not the child schema. This generates code in java where the required property on the schema property in the child is false when it should be true.

Swagger-codegen version

3.0.22

Swagger declaration file content or url

allOf:
  - $ref: '#/definitions/Base'
properties:
  uuidProp:
    type: string
    format: uuid
  stringProp:
    type: string
required:
  - uuidProp
  - stringProp

where Base

properties:
  baseProp:
    type: string
required: 
  - baseProp

Command line used for generation

Steps to reproduce

generate swagger code targeting java using the above yaml using javax bean validation.

note that the pojo validation for the generated schema objects are not properly including the @NotNull validation annotation.

Related issues/PRs

Suggest a fix/enhancement

Reproduce Java generation with the supplied allOf/required YAML and javax bean validation settings, then inspect the generated schema objects for the child properties. Confirm the issue by checking whether uuidProp and stringProp lack @NotNull while baseProp is handled. Done means child-schema required properties generate the expected @NotNull validation annotations.