Endpoints with only 3xx responses are rejected as invalid (no generated method) #413

Description

When using openapi-processor-spring, operations that only declare redirect
responses (e.g. HTTP 302) are considered invalid and are not generated in the
Spring interface.

The processor reports an error similar to

endpoint '/logout' has no success 2xx response.

As a result, no method is generated for the endpoint.

Example OpenAPI

### Example OpenAPI

```yaml
/authorize:
  get:
    summary: OAuth2 authorize endpoint
    responses:
      '302':
        description: Redirect to authorization server
        headers:
          Location:
            schema:
              type: string

This OpenAPI definition is valid and accurately describes the runtime behavior:
the endpoint always responds with a redirect and never returns a 2xx response.

Actual behaviour:

• The processor reports a validation error: endpoint has no success 2xx response
• No method is generated in the Spring interface

Expected behaviour:

The processor should generate the endpoint method even if the operation only
defines 3xx responses.

Redirect-based endpoints are a valid and common HTTP pattern, especially in
browser-based flows such as:

• OAuth2 /authorize
• login / logout endpoints
• SSO / identity provider redirects

Requiring an artificial 2xx response (e.g. a dummy 204) just to satisfy the
generator leads to OpenAPI specifications that do not accurately reflect
runtime behavior.