(core) Add optional telemetry to grist-core

Summary:
Adds support for optional telemetry to grist-core.

A new environment variable, GRIST_TELEMETRY_LEVEL, controls the level of telemetry collected.

Test Plan: Server and unit tests.

Reviewers: paulfitz

Reviewed By: paulfitz

Subscribers: dsagal, anaisconce

Differential Revision: https://phab.getgrist.com/D3880

app/server/lib/DocApi.ts

@@ -916,8 +916,10 @@ export class DocWorkerApi {
           });
           const {forkId} = parseUrlId(scope.urlId);
           activeDoc.logTelemetryEvent(docSession, 'tutorialRestarted', {
-            tutorialForkIdDigest: forkId ? hashId(forkId) : undefined,
-            tutorialTrunkIdDigest: hashId(tutorialTrunkId),
+            full: {
+              tutorialForkIdDigest: forkId ? hashId(forkId) : undefined,
+              tutorialTrunkIdDigest: hashId(tutorialTrunkId),
+            },
           });
         }
       }