Add frontend spec

frontend/spec/lib/api.md

@@ -0,0 +1,25 @@
+The api allows the frontend to access the database. Most endpoints are authenticated using NIP 98.
+
+## `class ApiError`
+
+- This is a custom error class with an additional `status` property
+
+## `function makeAuth<T>()`
+
+- If the user is not currently logged in, returns undefined
+- Otherwise, builds an NIP 98 auth header with no `method` and `u` set to `VITE_API_URL`. This is non-standard, but intentional in order to prevent repeated signer authorizations.
+- This function is memoized over pubkey and expires after 10 minutes.
+- Returns the full `Authorization` header value.
+
+## `function callApi<T>(method: string, path: string, body?: T)`
+
+- Uses `makeAuth` to obtain a NIP 98 authorization header.
+- Calls the backend api and returns the decoded json or throws an `ApiError`.
+
+## `function get(path: string)`
+
+- Calls `callApi` with `get`
+
+## `function post<T>(path: string, body: T)`
+
+- Calls `callApi` with `post` and body