assistant: Add Mistral support (#24879)

Closes #12519.

Release Notes:

- Added support for Mistral to the Assistant.

---------

Co-authored-by: Marshall Bowers <git@maxdeviant.com>

crates/language_model/Cargo.toml

@@ -28,6 +28,7 @@ http_client.workspace = true
 image.workspace = true
 lmstudio = { workspace = true, features = ["schemars"] }
 log.workspace = true
+mistral = { workspace = true, features = ["schemars"] }
 ollama = { workspace = true, features = ["schemars"] }
 open_ai = { workspace = true, features = ["schemars"] }
 parking_lot.workspace = true

crates/language_model/src/request.rs

@@ -269,6 +269,47 @@ impl LanguageModelRequest {
         }
     }
 
+    pub fn into_mistral(self, model: String, max_output_tokens: Option<u32>) -> mistral::Request {
+        let len = self.messages.len();
+        let merged_messages =
+            self.messages
+                .into_iter()
+                .fold(Vec::with_capacity(len), |mut acc, msg| {
+                    let role = msg.role;
+                    let content = msg.string_contents();
+
+                    acc.push(match role {
+                        Role::User => mistral::RequestMessage::User { content },
+                        Role::Assistant => mistral::RequestMessage::Assistant {
+                            content: Some(content),
+                            tool_calls: Vec::new(),
+                        },
+                        Role::System => mistral::RequestMessage::System { content },
+                    });
+                    acc
+                });
+
+        mistral::Request {
+            model,
+            messages: merged_messages,
+            stream: true,
+            max_tokens: max_output_tokens,
+            temperature: self.temperature,
+            response_format: None,
+            tools: self
+                .tools
+                .into_iter()
+                .map(|tool| mistral::ToolDefinition::Function {
+                    function: mistral::FunctionDefinition {
+                        name: tool.name,
+                        description: Some(tool.description),
+                        parameters: Some(tool.input_schema),
+                    },
+                })
+                .collect(),
+        }
+    }
+
     pub fn into_google(self, model: String) -> google_ai::GenerateContentRequest {
         google_ai::GenerateContentRequest {
             model,