collab: Add GET /models endpoint to LLM service (#17307)

This PR adds a `GET /models` endpoint to the LLM service.

This endpoint returns the models that the authenticated user has access
to.

This is the first step towards populating the models for the hosted
service from the server.

Release Notes:

- N/A

crates/collab/src/llm/authorization.rs

@@ -7,7 +7,7 @@ use crate::{Config, Error, Result};
 pub fn authorize_access_to_language_model(
     config: &Config,
     claims: &LlmTokenClaims,
-    country_code: Option<String>,
+    country_code: Option<&str>,
     provider: LanguageModelProvider,
     model: &str,
 ) -> Result<()> {
@@ -49,7 +49,7 @@ fn authorize_access_to_model(
 
 fn authorize_access_for_country(
     config: &Config,
-    country_code: Option<String>,
+    country_code: Option<&str>,
     provider: LanguageModelProvider,
 ) -> Result<()> {
     // In development we won't have the `CF-IPCountry` header, so we can't check
@@ -62,7 +62,7 @@ fn authorize_access_for_country(
     }
 
     // https://developers.cloudflare.com/fundamentals/reference/http-request-headers/#cf-ipcountry
-    let country_code = match country_code.as_deref() {
+    let country_code = match country_code {
         // `XX` - Used for clients without country code data.
         None | Some("XX") => Err(Error::http(
             StatusCode::BAD_REQUEST,
@@ -128,7 +128,7 @@ mod tests {
             authorize_access_to_language_model(
                 &config,
                 &claims,
-                Some(country_code.into()),
+                Some(country_code),
                 provider,
                 "the-model",
             )
@@ -178,7 +178,7 @@ mod tests {
             let error_response = authorize_access_to_language_model(
                 &config,
                 &claims,
-                Some(country_code.into()),
+                Some(country_code),
                 provider,
                 "the-model",
             )
@@ -223,7 +223,7 @@ mod tests {
             let error_response = authorize_access_to_language_model(
                 &config,
                 &claims,
-                Some(country_code.into()),
+                Some(country_code),
                 provider,
                 "the-model",
             )
@@ -278,13 +278,8 @@ mod tests {
                 ..Default::default()
             };
 
-            let result = authorize_access_to_language_model(
-                &config,
-                &claims,
-                Some("US".into()),
-                provider,
-                model,
-            );
+            let result =
+                authorize_access_to_language_model(&config, &claims, Some("US"), provider, model);
 
             if expected_access {
                 assert!(
@@ -324,13 +319,8 @@ mod tests {
         ];
 
         for (provider, model) in test_cases {
-            let result = authorize_access_to_language_model(
-                &config,
-                &claims,
-                Some("US".into()),
-                provider,
-                model,
-            );
+            let result =
+                authorize_access_to_language_model(&config, &claims, Some("US"), provider, model);
 
             assert!(
                 result.is_ok(),

crates/collab/src/llm/db.rs

@@ -67,6 +67,14 @@ impl LlmDatabase {
         Ok(())
     }
 
+    /// Returns the list of all known models, with their [`LanguageModelProvider`].
+    pub fn all_models(&self) -> Vec<(LanguageModelProvider, model::Model)> {
+        self.models
+            .iter()
+            .map(|((model_provider, _model_name), model)| (*model_provider, model.clone()))
+            .collect::<Vec<_>>()
+    }
+
     /// Returns the names of the known models for the given [`LanguageModelProvider`].
     pub fn model_names_for_provider(&self, provider: LanguageModelProvider) -> Vec<String> {
         self.models