Multiple specs are not supported

[mzbik]

Adding a second api spec (per express-openapi-validator/examples/2-standard-multiple-api-specs), results in API returns from the second set of API being validated against the schema in the first set.

This is easily reproducible by editing express-openapi-validator/examples/2-standard-multiple-api-specs/app.js to enable response validation. E.g.,

  app.use(
    OpenApiValidator.middleware({
      apiSpec: apiSpec,
      validateResponses: true,
    }),
  );

Running curl 'localhost:3000/v2/pets?pet_type=kitty' | jq shows schema violations reported against the v1 schema:

{
  "message": ".response[0] should have required property 'id', .response[0] should have required property 'name', .response[0] should have required property 'type'",
  "errors": [
    {
      "path": ".response[0].id",
      "message": "should have required property 'id'",
      "errorCode": "required.openapi.validation"
    },
    {
      "path": ".response[0].name",
      "message": "should have required property 'name'",
      "errorCode": "required.openapi.validation"
    },
    {
      "path": ".response[0].type",
      "message": "should have required property 'type'",
      "errorCode": "required.openapi.validation"
    }
  ]
}

Note: I encountered this in my project where an embedded $ref was used to look up a schema against a set of paths from a >previous< apiDoc.

[mzbik]

Dup of #881