Move Community's graceful shutdown onto openvibe-sdk/service (#8)

ddiff --git a/test/service-kit.test.js b/test/service-kit.test.js
nnew file mode 100644
iindex 0000000..a4c4d65
---- /dev/null
++++ b/test/service-kit.test.js
@@@ -0,0 +1,37 @@
++'use strict';
++// Check the SDK graceful stop primitive used by Community. shutdown.test.js covers
++// the wiring and shutdown behavior on the real server.
++//   node test/service-kit.test.js
++const assert = require('assert');
++const http = require('http');
++const { gracefulStop, within } = require('openvibe-sdk/service');
++
++(async () => {
++    const server = http.createServer((req, res) => { res.end('ok'); });
++    await new Promise((r) => server.listen(0, '127.0.0.1', r));
++    const order = [];
++    let code = null;
++    const { stop, stopping } = gracefulStop({
++        name: 'ServiceKit', server, drainMs: 4000, deadlineMs: 5000, deadlineExitCode: 1, signals: false,
++        exit: (c) => { code = c; },
++        stop: [() => order.push('stop:one'), async () => order.push('stop:two')],
++        close: [() => order.push('close:one'), async () => order.push('close:two')],
++    });
++    assert.strictEqual(stopping(), false, 'not stopping before the signal');
++    const stopped = await stop('SIGTERM');
++    assert.deepStrictEqual(order, ['stop:one', 'stop:two', 'close:one', 'close:two'], 'the stop then close steps run in order');
++    assert.strictEqual(code, 0, 'a clean stop exits 0');
++    assert.strictEqual(stopped, 0, 'stop() resolves with the exit code');
++    assert.strictEqual(stopping(), true, 'stopping() is true once stop() has run');
++
++    // within() bounds a step and swallows its rejection (a best-effort stop step is never a reason to fail the stop).
++    // gracefulStop closed the server above, so keep the loop alive while the unref'd within timer fires.
++    const keepAlive = setInterval(() => {}, 1000);
++    const t0 = Date.now();
++    await within(50, new Promise(() => {}));
++    assert.ok(Date.now() - t0 < 2000, 'within returns at its bound');
++    await within(50, Promise.reject(new Error('a slow step rejected')));
++    clearInterval(keepAlive);
++
++    console.log('service-kit: all checks passed');
++})().catch((err) => { console.error(err); process.exitCode = 1; });