Splitted specification leads to unresolved references

[tmartin-git]

I have created a project to illustrate the problem: https://github.com/tmartin-git/oapi-codegen-unresolvedrefs

In short, if you have a splitted specification (components in a seperate yaml file) and have a schema that references another schema, then this second one does not appear in the generated spec embedded inside the go code (base64 gzip encoded).

Here is a specification excerpt (components is defined in a seperate file):

components:
  schemas:
    Pet:
      allOf:
        - $ref: '#/components/schemas/NewPet'
        - required:
            - id
          properties:
            id:
              type: integer
              format: int64
              description: Unique id of the pet
            PetExtra:
              $ref: '#/components/schemas/PetExtra'
    PetExtra:
      type: string
      description: PetExtra description

<truncated>
`

This leads to a failure when validation occurs and you get this kind of error message  :

`msg="failed to resolve \"configuration_api\" in fragment in URI: \"#/components/schemas/configuration_api\": map key \"configuration_api\" not found`