generateValidCase

Constructs a valid positive test case that satisfies required parameters, request body, and security requirements (when applicable).

Behavior:

• Only required parameters are populated (path/query/header/cookie).

• Parameter schema resolution uses schema first; if absent, falls back to content schema.

• Request body uses the first supported media type with example(s) or a schema.

• Success status code is the first 2xx response, then 2XX, then default if present.

• Security uses the first security requirement object if multiple are defined.