add `ai_model` support in deck for the ai-gateway

[Prashansa-K]

Schema: https://github.com/Kong/kong-ee/blob/85aeb4b0beb2da13e4acb040f758a8a3d3cc0df2/kong/db/schema/entities/ai_models.lua

[oowl]

team-ai-gateway ticket: First-class AI Model entity