[2/2] feat: report whether the calling account can use each generation model

paths/models.yaml

@@ -10,6 +10,9 @@
 
         Option schemas are omitted by default. Request them with `expand=options`.
 
+        Each model's `available` reflects the plan of the account behind the calling API
+        key, so offer only the models it marks available.
+
         **Base URL:** <a href="#">https://api.shotstack.io/edit/{version}</a>
       summary: List Generation Models
       operationId: getModels

schemas/generationmodel.yaml

@@ -39,6 +39,25 @@
             schema are rejected.
           type: object
           additionalProperties: true
+        available:
+          description: >-
+            Whether the account behind the calling API key can generate with this model.
+            Omitted when that cannot be determined; treat a missing value as unknown, not
+            as available. Generation requests are checked either way.
+          type: boolean
+          example: false
+        unavailableReason:
+          description: >-
+            Why `available` is false. `AiCapabilityNotIncluded`: the account's plan does
+            not include this kind of generation. `AiDisabled`: AI generation is turned
+            off for the account. `AiAccessUnavailable`: access could not be confirmed;
+            try again later.
+          type: string
+          enum:
+            - AiCapabilityNotIncluded
+            - AiDisabled
+            - AiAccessUnavailable
+          example: AiCapabilityNotIncluded
       required:
         - model
         - type