Record model and cost when reporting logs (#136)

* Rename prompt and completion tokens to input and output tokens

* Add getUsage function

* Record model and cost when reporting log

* Remove unused imports

* Move UsageGraph to its own component

* Standardize model response fields

* Fix types

app/src/modelProviders/anthropic-completion/index.ts

@@ -28,6 +28,10 @@ const modelProvider: AnthropicProvider = {
   inputSchema: inputSchema as JSONSchema4,
   canStream: true,
   getCompletion,
+  getUsage: (input, output) => {
+    // TODO: add usage logic
+    return null;
+  },
   ...frontendModelProvider,
 };