chore(api): document API error response contracts

Castiron-Internal-PR: openai/openai-python-internal#122
Castiron-Source-SHA: 63257befa8e171dc627efa016481ca0d6ccd4ade
Castiron-Public-Base-SHA: 69a2c1d

Author: markstuart-oai

.castiron.stats.yml

@@ -1,8 +1,8 @@
 schema_version: 1
-generation_id: feaf88e6-0c6a-4d57-95a5-0bcc23d7105c
-openapi_spec_hash: ce912f79d7f8cb19a7a515513c214b8a
-openapi_transformed_spec_hash: 352b5a7a028f990b6475b6593e381eee
-config_hash: dde98d9c41cd6f4163320f92c70f83e6
-codegen_sha: 799a1f4d5f6b415088641ca4d3bbb804443ec30e
+generation_id: 3302daca-12b8-44d9-9ee3-dff23b6c8cd4
+openapi_spec_hash: 662efe7cf7d92cb2a9e77bef4bfbe722
+openapi_transformed_spec_hash: 8d8bd62278396a9cdfbbb49177613b11
+config_hash: e9f2f75046b7218f4e0d78f7db7b7909
+codegen_sha: ca034bfdf2e2c00f76d152f1eef154a2825d1d67
 codegen_hash: 7d4da50897149f4eab2fa63ac3dbc972694c6dfeb79a01531da408010bff5dcd
-public_codegen_sha: 4b121f228fc198913ea2a56404f38d8f18ca0e86
+public_codegen_sha: d97ff2bcd11f6cac7432b0d90ac8aac292c03a94