(core) add minimal support for activation keys

Summary: For grist-ee, expect an activation key in environment variable `GRIST_ACTIVATION` or in a file pointed to by `GRIST_ACTIVATION_FILE`. In absence of key, start a 30-day trial, during which a banner is shown. Once trial expires, installation goes into document-read-only mode.

Test Plan: added a test

Reviewers: dsagal

Reviewed By: dsagal

Subscribers: jarek

Differential Revision: https://phab.getgrist.com/D3426

app/server/lib/FlexServer.ts

@@ -12,6 +12,7 @@ import {ApiServer} from 'app/gen-server/ApiServer';
 import {Document} from "app/gen-server/entity/Document";
 import {Organization} from "app/gen-server/entity/Organization";
 import {Workspace} from 'app/gen-server/entity/Workspace';
+import {Activations} from 'app/gen-server/lib/Activations';
 import {DocApiForwarder} from 'app/gen-server/lib/DocApiForwarder';
 import {getDocWorkerMap} from 'app/gen-server/lib/DocWorkerMap';
 import {HomeDBManager} from 'app/gen-server/lib/HomeDBManager';
@@ -470,6 +471,9 @@ export class FlexServer implements GristServer {
     await this._dbManager.initializeSpecialIds();
     // Report which database we are using, without sensitive credentials.
     this.info.push(['database', getDatabaseUrl(this._dbManager.connection.options, false)]);
+    // If the installation appears to be new, give it an id and a creation date.
+    const activations = new Activations(this._dbManager);
+    await activations.current();
   }
 
   public addDocWorkerMap() {
@@ -566,6 +570,12 @@ export class FlexServer implements GristServer {
     this._billing.addEventHandlers();
   }
 
+  public async addBillingMiddleware() {
+    if (this._check('activation', 'homedb')) { return; }
+    this._getBilling();
+    await this._billing.addMiddleware?.(this.app);
+  }
+
   /**
    * Add a /api/log endpoint that simply outputs client errors to our
    * logs.  This is a minimal placeholder for a special-purpose