feat: support multiple ngit-grasp instances in NixOS module

- Convert module from single service to attrsOf instances
- Each instance gets separate systemd service: ngit-grasp-<name>
- Each instance gets separate user: ngit-grasp-<name> (customizable)
- Default dataDir per instance: /var/lib/ngit-grasp-<name>
- Update example to show single and multiple instance configs
- Add notes on systemd service management per instance

1 files changed, 93 insertions, 18 deletions

diff --git a/nix/example-configuration.nix b/nix/example-configuration.nix
index a00d970..34615be 100644
--- a/nix/example-configuration.nix
+++ b/nix/example-configuration.nix
@@ -1,4 +1,4 @@
-# Example NixOS configuration using ngit-grasp module
+# Example NixOS configurations using ngit-grasp module
 # 
 # Usage:
 #   1. Add to your server's flake.nix inputs:
@@ -7,48 +7,54 @@
 #   2. Import the module in your configuration:
 #      imports = [ inputs.ngit-grasp.nixosModules.default ];
 #
-#   3. Configure the service (example below)
+#   3. Configure one or more instances (examples below)
 
 { inputs, ... }:
 
 {
   imports = [ inputs.ngit-grasp.nixosModules.default ];
 
-  services.ngit-grasp = {
+  # ============================================================================
+  # EXAMPLE 1: Single Instance Configuration
+  # ============================================================================
+
+  services.ngit-grasp.production = {
     enable = true;
     domain = "ngit.danconwaydev.com";
-    
+
     # Network
     bindAddress = "127.0.0.1";
-    port = 8082;  # Same port as current ngit-relay for Caddy compatibility
-    
-    # Storage (reuse existing persistent path pattern)
+    port = 8082;
+
+    # Storage
     dataDir = "/persistent/ngit-danconwaydev-com-ngit-grasp";
-    
+
     # Identity
     relayName = "DanConwayDev's ngit-grasp";
-    relayDescription = "personal instance of ngit-grasp, a Rust GRASP implementation with proactive sync";
-    
+    relayDescription =
+      "personal instance of ngit-grasp, a Rust GRASP implementation with proactive sync";
+
     # Option 1: Use nsec file (recommended - more secure)
-    relayOwnerNsecFile = "/persistent/ngit-danconwaydev-com-ngit-grasp/relay-owner.nsec";
-    
+    relayOwnerNsecFile =
+      "/persistent/ngit-danconwaydev-com-ngit-grasp/relay-owner.nsec";
+
     # Option 2: Inline nsec (less secure, ends up in nix store)
     # relayOwnerNsec = "nsec1...";
-    
+
     # Option 3: Auto-generate (default if neither above is set)
     # ngit-grasp will create .relay-owner.nsec in dataDir automatically
-    
+
     # Sync
     syncBootstrapRelayUrl = "wss://relay.ngit.dev";
-    
+
     # Metrics
     metricsEnabled = true;
-    
+
     # Logging
-    logLevel = "info";  # Options: trace, debug, info, warn, error
+    logLevel = "info"; # Options: trace, debug, info, warn, error
   };
 
-  # Caddy reverse proxy (unchanged from current setup)
+  # Caddy reverse proxy for production instance
   services.caddy.virtualHosts."ngit.danconwaydev.com" = {
     extraConfig = ''
       reverse_proxy 127.0.0.1:8082 {
@@ -57,4 +63,73 @@
       }
     '';
   };
+
+  # ============================================================================
+  # EXAMPLE 2: Multiple Instances on Same Server
+  # ============================================================================
+
+  # Uncomment to run multiple instances:
+
+  # # Production instance
+  # services.ngit-grasp.prod = {
+  #   enable = true;
+  #   domain = "ngit.example.com";
+  #   port = 8082;
+  #   dataDir = "/persistent/ngit-production";
+  #   relayName = "Production GRASP Relay";
+  #   syncBootstrapRelayUrl = "wss://relay.ngit.dev";
+  #   logLevel = "info";
+  # };
+  # 
+  # # Testing/staging instance
+  # services.ngit-grasp.staging = {
+  #   enable = true;
+  #   domain = "ngit-staging.example.com";
+  #   port = 8083;
+  #   dataDir = "/persistent/ngit-staging";
+  #   relayName = "Staging GRASP Relay";
+  #   syncBootstrapRelayUrl = "wss://relay.ngit.dev";
+  #   logLevel = "debug";  # More verbose logging for testing
+  # };
+  # 
+  # # Development instance with in-memory database
+  # services.ngit-grasp.dev = {
+  #   enable = true;
+  #   domain = "localhost";
+  #   bindAddress = "127.0.0.1";
+  #   port = 8084;
+  #   dataDir = "/tmp/ngit-dev";
+  #   databaseBackend = "memory";  # No persistence
+  #   relayName = "Development GRASP Relay";
+  #   metricsEnabled = false;
+  #   logLevel = "trace";  # Maximum verbosity for debugging
+  # };
+  # 
+  # # Caddy configuration for multiple instances
+  # services.caddy.virtualHosts = {
+  #   "ngit.example.com" = {
+  #     extraConfig = "reverse_proxy 127.0.0.1:8082";
+  #   };
+  #   "ngit-staging.example.com" = {
+  #     extraConfig = "reverse_proxy 127.0.0.1:8083";
+  #   };
+  # };
+
+  # ============================================================================
+  # NOTES
+  # ============================================================================
+
+  # Instance names (e.g., "production", "prod", "staging") can be anything.
+  # They are used for:
+  #   - systemd service names: ngit-grasp-<name>
+  #   - default user names: ngit-grasp-<name>
+  #   - default data directories: /var/lib/ngit-grasp-<name>
+
+  # Systemd service management:
+  #   systemctl status ngit-grasp-production
+  #   systemctl restart ngit-grasp-staging
+  #   journalctl -u ngit-grasp-prod -f
+
+  # Each instance runs as a separate user but shares the same group by default.
+  # You can customize user/group per instance if needed.
 }