lint: non-existing object properties listed as required are ignored

Describe the bug The openapi-cli ignores non-existing object properties which are listed as required. Anything can be listed under the required: tag and the lint will not return any errors.

To Reproduce Steps to reproduce the behavior:

1. Use the example petstore.yaml (the behaviour is the same with 2.0, 3.0 and 3.1)
2. Add a non-existing or rename an existing required property:

diff --git a/petstore.yaml b/petstore.yaml
index 5f41fe0..531cbbf 100644
--- a/petstore.yaml
+++ b/petstore.yaml
@@ -78,6 +78,7 @@ definitions:
     required:
       - id
       - name
+      - non-existing-property
     properties:
       id:
         type: integer

1. Run openapi lint petstore.yaml --format stylish
2. The output is:

No configurations were defined in extends -- using built-in recommended configuration by default.

validating petstore.yaml...
petstore.yaml:
  2:1   warning  info-description        Info object should contain `description` field.
  5:3   warning  info-license-url        License object should contain `url` field.
  29:7  warning  operation-4xx-response  Operation must have at least one `4xx` response.
  47:7  warning  operation-4xx-response  Operation must have at least one `4xx` response.
  66:7  warning  operation-4xx-response  Operation must have at least one `4xx` response.

petstore.yaml: validated in 26ms

Woohoo! Your OpenAPI definition is valid. 🎉
You have 5 warnings.

1. The exit code:

$ echo $?
0

Expected behavior There should be an error saying the required property is not defined, for example:

"non-existing-property" is present in required but not defined as property in definition "Pet"

openapi-cli Version(s)

$ openapi --version
1.0.0-beta.73

Node.js Version(s)

$ node --version
v17.2.0

Additional context

• The behaviour is the same with all OpenAPI versions.
• There is no .redocly.yaml present, the default out-of-the-box openapi-cli is used.
• The same can be observed using the latest NPM and Docker versions.

[davidkuridza]

@tatomyr no problem, good things come to those who wait 😃

[adamaltman]

@davidkuridza finally in progress on this one. 👍