fix: Callback component $$ref handling (#4454)

test/e2e/specs/bugs/4445.yaml

@@ -0,0 +1,64 @@
+openapi: 3.0.0
+info:
+  title: Callback Example
+  version: 1.0.0
+paths:
+  /streams:
+    post:
+      description: subscribes a client to receive out-of-band data
+      parameters:
+        - name: callbackUrl
+          in: query
+          required: true
+          description: |
+            the location where data will be sent.  Must be network accessible
+            by the source server
+          schema:
+            type: string
+            format: uri
+            example: https://tonys-server.com
+      responses:
+        '201':
+          description: subscription successfully created
+          content:
+            application/json:
+              schema:
+                description: subscription information
+                required:
+                  - subscriptionId
+                properties:
+                  subscriptionId:
+                    description: this unique identifier allows management of the subscription
+                    type: string
+                    example: 2531329f-fb09-4ef7-887e-84e648214436
+      callbacks:
+        # the name `onData` is a convenience locator
+        onData:
+          $ref: '#/components/callbacks/onData'
+components:
+  callbacks:
+    onData:
+      # when data is sent, it will be sent to the `callbackUrl` provided
+      # when making the subscription PLUS the suffix `/data`
+      '{$request.query.callbackUrl}/data':
+        post:
+          requestBody:
+            description: subscription payload
+            content:
+              application/json:
+                schema:
+                  properties:
+                    timestamp:
+                      type: string
+                      format: date-time
+                    userData:
+                      type: string
+          responses:
+            '202':
+              description: |
+                Your server implementation should return this HTTP status code
+                if the data was received successfully
+            '204':
+              description: |
+                Your server should return this HTTP status code if no longer interested
+                in further updates