Split Core modules into separate files

PluralKit.Core/Modules/MetricsModule.cs

@@ -0,0 +1,32 @@
+using App.Metrics;
+
+using Autofac;
+
+namespace PluralKit.Core
+{
+    public class MetricsModule: Module
+    {
+        private readonly string _onlyContext;
+
+        public MetricsModule(string onlyContext = null)
+        {
+            _onlyContext = onlyContext;
+        }
+
+        protected override void Load(ContainerBuilder builder)
+        {
+            builder.Register(c => InitMetrics(c.Resolve<CoreConfig>()))
+                .AsSelf().As<IMetrics>().SingleInstance();
+        }
+
+        private IMetricsRoot InitMetrics(CoreConfig config)
+        {
+            var builder = AppMetrics.CreateDefaultBuilder();
+            if (config.InfluxUrl != null && config.InfluxDb != null)
+                builder.Report.ToInfluxDb(config.InfluxUrl, config.InfluxDb);
+            if (_onlyContext != null)
+                builder.Filter.ByIncludingOnlyContext(_onlyContext);
+            return builder.Build();
+        }
+    }
+}