feat(services): added postgres service

services-flake is used to provide services the application needs to run.
For now, this includes postgres which can be used for data storage going
forward. Use `nix run .#services` to launch process-compose which will
spin up the services.

The http server also depends on a lockpad server being present but this
is not ran through the services at this time. Instead lockpad has its
own `services` package which functions the same way.

Environment variables have been added that are used to configure
dependent services:
- `PRJ_DATA_HOME` - where to persist service data (recommend: set to the
 absolute path to the `.data` subdirectory of this repo)
- `ANNAPURNA_POSTGRES_PORT` - determines the port to use (note, this is
  disabled via commenting `listen_port`, but the name is reserved)

.gitignore

@@ -5,3 +5,4 @@ result*
 target
 
 .static
+.data

flake-parts/postgres.nix

@@ -0,0 +1,14 @@
+{...} @ part-inputs: {
+  imports = [];
+
+  perSystem = {
+    pkgs,
+    inputs',
+    self',
+    ...
+  }: {
+    packages = {
+      postgresql = inputs'.nix-postgres.packages."psql_15/bin";
+    };
+  };
+}

flake-parts/services.nix

@@ -0,0 +1,45 @@
+{inputs, ...} @ part-inputs: {
+  imports = [];
+
+  perSystem = {
+    pkgs,
+    inputs',
+    self',
+    ...
+  }: let
+    ports = {
+      annapurna-postgres = "\${ANNAPURNA_POSTGRES_PORT}";
+    };
+
+    global-imports = [
+      ({name, ...}: {
+        dataDirEnv = "\${PRJ_DATA_HOME}/${name}";
+        socketDirEnv = "\${PRJ_DATA_HOME}/${name}/sockets";
+      })
+    ];
+  in rec {
+    process-compose = {
+      services = {
+        imports = [
+          inputs.services-flake.processComposeModules.default
+        ];
+
+        services.postgres."annapurna-postgres" = {
+          imports = global-imports;
+
+          enable = true;
+          package = self'.packages.postgresql;
+
+          # by not including a listen address, we only listen on the unix socket
+          # listen_addresses = "127.0.0.1";
+          port = ports.annapurna-postgres;
+          initialDatabases = [
+            {
+              name = "annapurna-local";
+            }
+          ];
+        };
+      };
+    };
+  };
+}

flake-parts/shells.nix

@@ -8,7 +8,7 @@
     lib,
     ...
   }: let
-    inherit (self'.packages) rust-toolchain;
+    inherit (self'.packages) rust-toolchain postgresql;
     inherit (self'.legacyPackages) cargoExtraPackages ciPackages;
 
     devTools = [
@@ -21,6 +21,8 @@
       pkgs.wasm-bindgen-cli
       # formatting
       self'.packages.treefmt
+
+      postgresql
     ];
   in {
     devShells = {