a couple of representation tweaks for codegen (Azure#24847)

Author: trrwilson

specification/cognitiveservices/OpenAI.Inference/models/chat.completions.tsp

@@ -32,9 +32,10 @@ model ChatMessage {
   @projectedName("json", "role")
   role: ChatRole;
 
+  #suppress "@azure-tools/typespec-azure-core/no-nullable" "we explicitly want a nullable string"
   @doc("The text associated with this message payload.")
   @projectedName("json", "content")
-  content?: string;
+  content: string | null;
 
   @doc("""
     The name of the author of this message. `name` is required if role is `function`, and it should be the name of the
@@ -225,9 +226,9 @@ model ChatCompletions {
     represented as seconds since the beginning of the Unix epoch of 00:00 on 1 Jan 1970.
     """)
   @projectedName("json", "created")
-  @projectedName("csharp", "InternalCreatedSecondsAfterUnixEpoch")
   @projectedName("java", "createdAt")
-  created: int32;
+  @encode(DateTimeKnownEncoding.unixTimestamp, int32)
+  created: utcDateTime;
 
   @doc("""
     The collection of completions choices associated with this completions response.

specification/cognitiveservices/OpenAI.Inference/models/completions.create.tsp

@@ -158,8 +158,9 @@ model Completions {
     represented as seconds since the beginning of the Unix epoch of 00:00 on 1 Jan 1970.
     """)
   @projectedName("json", "created")
-  @projectedName("csharp", "InternalCreatedSecondsAfterUnixEpoch")
-  created: int32;
+  @projectedName("java", "createdAt")
+  @encode(DateTimeKnownEncoding.unixTimestamp, int32)
+  created: utcDateTime;
 
   @doc("""
   Content filtering results for zero or more prompts in the request. In a streaming request, 

specification/cognitiveservices/OpenAI.Inference/models/images.tsp

@@ -76,12 +76,13 @@ model ImagePayload {
 @added(ServiceApiVersions.v2023_06_01_Preview)
 model ImageGenerations {
   @doc("A timestamp when this job or item was created (in unix epochs).")
-  @projectedName("csharp", "InternalCreatedSecondsAfterUnixEpoch")
-  created: int64;
+  @projectedName("json", "created")
+  @projectedName("java", "createdAt")
+  @encode(DateTimeKnownEncoding.unixTimestamp, int32)
+  created: utcDateTime;
 
   #suppress "@azure-tools/typespec-autorest/union-unsupported" "openapi v2 not required"
   @doc("The images generated by the operator.")
-  @projectedName("csharp", "InternalEmittedImageResponseItems")
   data: ImageLocation[] | ImagePayload[];
 }
 
@@ -96,7 +97,10 @@ model BatchImageGenerationOperationResponse {
   id: string;
 
   @doc("A timestamp when this job or item was created (in unix epochs).")
-  created: int64;
+  @projectedName("json", "created")
+  @projectedName("java", "createdAt")
+  @encode(DateTimeKnownEncoding.unixTimestamp, int32)
+  created: utcDateTime;
 
   @doc("A timestamp when this operation and its associated images expire and will be deleted (in unix epochs).")
   expires?: int64;

specification/cognitiveservices/data-plane/AzureOpenAI/inference/preview/2023-06-01-preview/generated.json

@@ -421,7 +421,7 @@
         },
         "created": {
           "type": "integer",
-          "format": "int64",
+          "format": "unixtime",
           "description": "A timestamp when this job or item was created (in unix epochs)."
         },
         "expires": {
@@ -492,7 +492,7 @@
         },
         "created": {
           "type": "integer",
-          "format": "int32",
+          "format": "unixtime",
           "description": "The first timestamp associated with generation activity for this completions response,\nrepresented as seconds since the beginning of the Unix epoch of 00:00 on 1 Jan 1970."
         },
         "choices": {
@@ -613,11 +613,13 @@
         },
         "content": {
           "type": "string",
-          "description": "The text associated with this message payload."
+          "description": "The text associated with this message payload.",
+          "x-nullable": true
         }
       },
       "required": [
-        "role"
+        "role",
+        "content"
       ]
     },
     "ChatRole": {
@@ -702,7 +704,7 @@
         },
         "created": {
           "type": "integer",
-          "format": "int32",
+          "format": "unixtime",
           "description": "The first timestamp associated with generation activity for this completions response,\nrepresented as seconds since the beginning of the Unix epoch of 00:00 on 1 Jan 1970."
         },
         "prompt_annotations": {
@@ -1164,7 +1166,7 @@
       "properties": {
         "created": {
           "type": "integer",
-          "format": "int64",
+          "format": "unixtime",
           "description": "A timestamp when this job or item was created (in unix epochs)."
         },
         "data": {

specification/cognitiveservices/data-plane/AzureOpenAI/inference/preview/2023-07-01-preview/generated.json

@@ -421,7 +421,7 @@
         },
         "created": {
           "type": "integer",
-          "format": "int64",
+          "format": "unixtime",
           "description": "A timestamp when this job or item was created (in unix epochs)."
         },
         "expires": {
@@ -492,7 +492,7 @@
         },
         "created": {
           "type": "integer",
-          "format": "int32",
+          "format": "unixtime",
           "description": "The first timestamp associated with generation activity for this completions response,\nrepresented as seconds since the beginning of the Unix epoch of 00:00 on 1 Jan 1970."
         },
         "choices": {
@@ -625,7 +625,8 @@
         },
         "content": {
           "type": "string",
-          "description": "The text associated with this message payload."
+          "description": "The text associated with this message payload.",
+          "x-nullable": true
         },
         "name": {
           "type": "string",
@@ -638,7 +639,8 @@
         }
       },
       "required": [
-        "role"
+        "role",
+        "content"
       ]
     },
     "ChatRole": {
@@ -729,7 +731,7 @@
         },
         "created": {
           "type": "integer",
-          "format": "int32",
+          "format": "unixtime",
           "description": "The first timestamp associated with generation activity for this completions response,\nrepresented as seconds since the beginning of the Unix epoch of 00:00 on 1 Jan 1970."
         },
         "prompt_annotations": {
@@ -1235,7 +1237,7 @@
       "properties": {
         "created": {
           "type": "integer",
-          "format": "int64",
+          "format": "unixtime",
           "description": "A timestamp when this job or item was created (in unix epochs)."
         },
         "data": {

specification/cognitiveservices/data-plane/AzureOpenAI/inference/stable/2022-12-01/generated.json

@@ -271,7 +271,7 @@
         },
         "created": {
           "type": "integer",
-          "format": "int32",
+          "format": "unixtime",
           "description": "The first timestamp associated with generation activity for this completions response,\nrepresented as seconds since the beginning of the Unix epoch of 00:00 on 1 Jan 1970."
         },
         "choices": {

specification/cognitiveservices/data-plane/AzureOpenAI/inference/stable/2023-05-15/generated.json

@@ -314,7 +314,7 @@
         },
         "created": {
           "type": "integer",
-          "format": "int32",
+          "format": "unixtime",
           "description": "The first timestamp associated with generation activity for this completions response,\nrepresented as seconds since the beginning of the Unix epoch of 00:00 on 1 Jan 1970."
         },
         "choices": {
@@ -426,11 +426,13 @@
         },
         "content": {
           "type": "string",
-          "description": "The text associated with this message payload."
+          "description": "The text associated with this message payload.",
+          "x-nullable": true
         }
       },
       "required": [
-        "role"
+        "role",
+        "content"
       ]
     },
     "ChatRole": {
@@ -510,7 +512,7 @@
         },
         "created": {
           "type": "integer",
-          "format": "int32",
+          "format": "unixtime",
           "description": "The first timestamp associated with generation activity for this completions response,\nrepresented as seconds since the beginning of the Unix epoch of 00:00 on 1 Jan 1970."
         },
         "choices": {