feat: add debugger support for Cloud Run. See b/112087600 for context (#671)

(Partially) Fixes b/112087600.

[✓] Tests and linter pass
[✓] Code coverage does not decrease (if any source code was changed)
[✓] Appropriate docs were updated (if necessary)

Author: hrasadi

src/agent/debuglet.ts

@@ -274,8 +274,10 @@ export class Debuglet extends EventEmitter {
     const envConfig = {
       logLevel: process.env.GCLOUD_DEBUG_LOGLEVEL,
       serviceContext: {
-        service: process.env.GAE_SERVICE || process.env.GAE_MODULE_NAME,
-        version: process.env.GAE_VERSION || process.env.GAE_MODULE_VERSION,
+        service: process.env.GAE_SERVICE || process.env.GAE_MODULE_NAME ||
+            process.env.K_SERVICE,
+        version: process.env.GAE_VERSION || process.env.GAE_MODULE_VERSION ||
+            process.env.K_REVISION,
         minorVersion_:
             process.env.GAE_DEPLOYMENT_ID || process.env.GAE_MINOR_VERSION
       }

test/test-debuglet.ts

@@ -435,6 +435,20 @@ describe('Debuglet', () => {
                debuglet.config.serviceContext.version, 'fake-gae-version');
          });
 
+      it('should respect K_SERVICE and K_REVISION env. vars.', () => {
+        process.env.K_SERVICE = 'fake-cloudrun-service';
+        process.env.K_REVISION = 'fake-cloudrun-version';
+        const debug = new Debug({}, packageInfo);
+        const debuglet = new Debuglet(debug, defaultConfig);
+        assert.ok(debuglet.config);
+        assert.ok(debuglet.config.serviceContext);
+        assert.strictEqual(
+            debuglet.config.serviceContext.service, 'fake-cloudrun-service');
+        assert.strictEqual(
+            debuglet.config.serviceContext.version, 'fake-cloudrun-version');
+      });
+
+
       it('should respect FUNCTION_NAME env. var.', () => {
         process.env.FUNCTION_NAME = 'fake-fn-name';
         const debug = new Debug({}, packageInfo);