feat(server): add metric collection

src/server/api_metrics.v

@@ -0,0 +1,16 @@
+module server
+
+import metrics
+import web
+
+['/api/v1/metrics'; get]
+fn (mut app App) v1_metrics() web.Result {
+	mut exporter := metrics.new_prometheus_exporter([0.01, 0.05, 0.1, 0.5, 1, 100])
+	exporter.load(app.collector)
+	
+	// TODO stream to connection instead
+	body := exporter.export_to_string() or {
+		return app.status(.internal_server_error)
+	}
+	return app.body(.ok, 'text/plain', body)
+}

src/server/server.v

@@ -8,6 +8,7 @@ import util
 import db
 import build { BuildJobQueue }
 import cron.expression
+import metrics
 
 const (
 	log_file_name = 'vieter.log'
@@ -107,6 +108,7 @@ pub fn server(conf Config) ! {
 		repo: repo
 		db: db
 		job_queue: build.new_job_queue(global_ce, conf.base_image)
+		collector: metrics.new_default_collector()
 	}
 	app.init_job_queue() or {
 		util.exit_with_message(1, 'Failed to inialize job queue: $err.msg()')