Allow using a custom model when using zed.dev (#14933)

Release Notes:

- N/A

crates/anthropic/src/anthropic.rs

@@ -20,6 +20,12 @@ pub enum Model {
     Claude3Sonnet,
     #[serde(alias = "claude-3-haiku", rename = "claude-3-haiku-20240307")]
     Claude3Haiku,
+    #[serde(rename = "custom")]
+    Custom {
+        name: String,
+        #[serde(default)]
+        max_tokens: Option<usize>,
+    },
 }
 
 impl Model {
@@ -33,30 +39,41 @@ impl Model {
         } else if id.starts_with("claude-3-haiku") {
             Ok(Self::Claude3Haiku)
         } else {
-            Err(anyhow!("Invalid model id: {}", id))
+            Ok(Self::Custom {
+                name: id.to_string(),
+                max_tokens: None,
+            })
         }
     }
 
-    pub fn id(&self) -> &'static str {
+    pub fn id(&self) -> &str {
         match self {
             Model::Claude3_5Sonnet => "claude-3-5-sonnet-20240620",
             Model::Claude3Opus => "claude-3-opus-20240229",
             Model::Claude3Sonnet => "claude-3-sonnet-20240229",
             Model::Claude3Haiku => "claude-3-opus-20240307",
+            Model::Custom { name, .. } => name,
         }
     }
 
-    pub fn display_name(&self) -> &'static str {
+    pub fn display_name(&self) -> &str {
         match self {
             Self::Claude3_5Sonnet => "Claude 3.5 Sonnet",
             Self::Claude3Opus => "Claude 3 Opus",
             Self::Claude3Sonnet => "Claude 3 Sonnet",
             Self::Claude3Haiku => "Claude 3 Haiku",
+            Self::Custom { name, .. } => name,
         }
     }
 
     pub fn max_token_count(&self) -> usize {
-        200_000
+        match self {
+            Self::Claude3_5Sonnet
+            | Self::Claude3Opus
+            | Self::Claude3Sonnet
+            | Self::Claude3Haiku => 200_000,
+            Self::Custom { max_tokens, .. } => max_tokens.unwrap_or(200_000),
+        }
     }
 }
 
@@ -90,6 +107,7 @@ impl From<Role> for String {
 
 #[derive(Debug, Serialize)]
 pub struct Request {
+    #[serde(serialize_with = "serialize_request_model")]
     pub model: Model,
     pub messages: Vec<RequestMessage>,
     pub stream: bool,
@@ -97,6 +115,13 @@ pub struct Request {
     pub max_tokens: u32,
 }
 
+fn serialize_request_model<S>(model: &Model, serializer: S) -> Result<S::Ok, S::Error>
+where
+    S: serde::Serializer,
+{
+    serializer.serialize_str(&model.id())
+}
+
 #[derive(Serialize, Deserialize, Debug, Eq, PartialEq)]
 pub struct RequestMessage {
     pub role: Role,