Support COOKIE parameter location in OpenAPI spec parsing and code generation

[halotukozak]

Description

OpenAPI 3.0 defines 4 parameter locations: path, query, header, and cookie. Currently only path, query, and header are supported (ParameterLocation enum in ApiSpec.kt:46). Cookie parameters are silently dropped during parsing.

Acceptance criteria

• ParameterLocation enum includes COOKIE
• SpecParser correctly parses in: cookie parameters
• ClientGenerator generates cookie-setting code in Ktor requests
• Tests cover parsing and generation of cookie parameters