fix: external ref in schema definition

[AlexVarchuk]

What/Why/How?

fixes: #1862

Reference

Testing

openapi.yaml

openapi: 3.1.0
info:
  title: Try to reproduce
  version: 1.0.0
servers:
  - url: example.com
tags:
  - name: test
    x-displayName: The test Model
    description: |
      <SchemaDefinition schemaRef="#/components/schemas/test" />

paths:
  /newPath:
    post:
      requestBody:
        content: 
          application/json:
            schema:
              $ref: "#/components/schemas/test"
      responses:
        200:
          description: 'all ok'

components:
  schemas:
    test:
      $ref: ./test.yml#/Test

test.yaml

Test:
  type: object
  properties:
    test:
      type: string

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