docs: update README with install instructions

README.md

@@ -1,11 +1,32 @@
-Learning golang, writing a simple app to interface with an HTTP API and generate emailable reports from an actualbudget instance
+A simple Go service to generate and email reports on a schedule.
 
-# TODO
-- [x] Fetch the desired budget file
-- [x] Change path to route in API caller
-- [x] Trigger a bank sync and see if we can wait for it to finish (looks like it's a blocking call so we can safely sync before reports)
-- [x] Fetch the category information for each category as well as the overall groups
-- [x] Compile a email-friendly report of the information
-- [x] Send the email to the desired parties via SMTP
-- [x] Write flake derivation
-- [ ] Write flake module and systemd service
+# Installation (NixOS)
+If you're using NixOS we provide a simple flake module:
+
+```nix
+inputs.actualbudget-report.url = "git+https://git.wanderingcrow.net/TheWanderingCrow/actualbudget-report";
+```
+
+Then in your configuration (using sops-nix, you will need to adjust it if you use agenix or alternatives):
+```nix
+imports = [
+    inputs.actualbudget-report.nixosModules.default;
+];
+
+# Fill out all the following environment variables for the service
+sops.templates."actualbudget-report-env".content = ''
+    BASE_URL=
+    API_KEY=
+    SYNC_ID=
+    SMTP_USERNAME=
+    SMTP_PASSWORD=
+    SMTP_HOST=
+    SMTP_RECIPIENTS=
+'';
+
+services.actualbudget-report = {
+    enable = true;
+    interval = "Mon-Fri 12:00:00";
+    environmentFile = config.sops.templates."actualbudget-report-env".path;
+};
+```