Add 2023-05-15 api version for OpenAI (#23784)

Author: bexxx

specification/cognitiveservices/data-plane/AzureOpenAI/authoring/readme.md

@@ -4,7 +4,7 @@
 
 Configuration for generating AzureOpenAI SDK.
 
-The current release for the AzureOpenAI is `release_2022_12_01`.
+The current release for the AzureOpenAI is `release_2023_05_15`.
 
 ``` yaml
 tag: release_2022_12_01
@@ -85,3 +85,23 @@ directive:
   - suppress: IntegerTypeMustHaveFormat
     reason: API stewardship board recommend to use format "unixtime" which is not supported by linter at the moment. 
 ```
+
+## AzureOpenAI 2023-05-15
+These settings apply only when `--tag=release_2023_05_15` is specified on the command line.
+
+``` yaml $(tag) == 'release_2023_05_15'
+input-file: stable/2023-05-15/azureopenai.json
+```
+
+AutoRest-Linter Suppressions
+
+``` yaml
+# Ignore autorest-linter issues that cannot be resolved without breaking compatibility to existing openai api
+directive:
+  - suppress: DefinitionsPropertiesNamesCamelCase
+    reason: Existing external API uses property names like n_epochs, created_at, not following naming/casing guidelines from azure. 
+  - suppress: ValidFormats
+    reason: API stewardship board recommend to use format "unixtime" which is not supported by linter at the moment. 
+  - suppress: IntegerTypeMustHaveFormat
+    reason: API stewardship board recommend to use format "unixtime" which is not supported by linter at the moment. 
+```