feat: update image generation API to match latest OpenAI specs (#402)

* feat: update image generation API to match latest OpenAI specs

- Add ImageModeration enum with 'auto' (default) and 'low' values
- Add moderation parameter to CreateImageRequest for gpt-image-1
- Extend ImageQuality enum to support 'high', 'medium', 'low' for gpt-image-1

These changes align with the latest OpenAI API documentation for image generation.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

* add Auto to ImageQuality

---------

Co-authored-by: Claude <[email protected]>
Co-authored-by: Himanshu Neema <[email protected]>

Author: 3 people

async-openai/src/types/image.rs

@@ -57,6 +57,10 @@ pub enum ImageQuality {
     #[default]
     Standard,
     HD,
+    High,
+    Medium,
+    Low,
+    Auto,
 }
 
 #[derive(Debug, Serialize, Deserialize, Default, Clone, PartialEq)]
@@ -67,6 +71,14 @@ pub enum ImageStyle {
     Natural,
 }
 
+#[derive(Debug, Serialize, Deserialize, Default, Clone, PartialEq)]
+#[serde(rename_all = "lowercase")]
+pub enum ImageModeration {
+    #[default]
+    Auto,
+    Low,
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize, Default, Builder, PartialEq)]
 #[builder(name = "CreateImageRequestArgs")]
 #[builder(pattern = "mutable")]
@@ -110,6 +122,11 @@ pub struct CreateImageRequest {
     /// A unique identifier representing your end-user, which will help OpenAI to monitor and detect abuse. [Learn more](https://platform.openai.com/docs/usage-policies/end-user-ids).
     #[serde(skip_serializing_if = "Option::is_none")]
     pub user: Option<String>,
+
+    /// Control the content-moderation level for images generated by gpt-image-1.
+    /// Must be either `low` for less restrictive filtering or `auto` (default value).
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub moderation: Option<ImageModeration>,
 }
 
 #[derive(Debug, Deserialize, Serialize, Clone, PartialEq)]