dev: continue work on custom domains

Adds service for querying controlling user for a domain. If no user is
verified as allowed to control the domain then we give control to the
'admin' user (to support local configurations of Puter).

After this point, I find myself a bit stuck because DNS queries are
incredibly difficult to test locally when you use tailscale.

src/backend/exports.js

@@ -39,6 +39,9 @@ const { InternetModule } = require("./src/modules/internet/InternetModule.js");
 const { CaptchaModule } = require("./src/modules/captcha/CaptchaModule.js");
 const { EntityStoreModule } = require("./src/modules/entitystore/EntityStoreModule.js");
 const { KVStoreModule } = require("./src/modules/kvstore/KVStoreModule.js");
+const { ExternalExtrasModule } = require("./src/modules/external-extras/ExternalExtrasModule.js");
+const { FirebaseModule } = require("./src/modules/firebase/FirebaseModule.js");
+const { DomainModule } = require("./src/modules/domain/DomainModule.js");
 
 module.exports = {
     helloworld: () => {
@@ -64,6 +67,7 @@ module.exports = {
         CaptchaModule,
         EntityStoreModule,
         KVStoreModule,
+        DomainModule,
     ],
 
     // Pre-built modules

src/backend/src/modules/domain/DomainModule.js

@@ -0,0 +1,16 @@
+const { AdvancedBase } = require("@heyputer/putility");
+
+class DomainModule extends AdvancedBase {
+    async install (context) {
+        const services = context.get('services');
+
+        const { DomainVerificationService } = require('./DomainVerificationService');
+        services.registerService('domain-verification', DomainVerificationService);
+
+        // TODO: enable flag
+        const { TXTVerifyService } = require('./TXTVerifyService');
+        services.registerService('__txt-verify', TXTVerifyService);
+    }
+}
+
+module.exports = { DomainModule };

src/backend/src/modules/domain/DomainVerificationService.js

@@ -0,0 +1,26 @@
+const { get_user } = require("../../helpers");
+const BaseService = require("../../services/BaseService");
+
+class DomainVerificationService extends BaseService {
+    async get_controlling_user ({ domain }) {
+        const svc_event = this.services.get('event');
+        
+        // 1 :: Allow event listeners to verify domains
+        const event = {
+            domain,
+            user: undefined,
+        };
+        await svc_event.emit('domain.get-controlling-user', event);
+        if ( event.user ) {
+            return event.user;
+        }
+        
+        // 2 :: If there is no controlling user, 'admin' is the
+        //      controlling user.
+        return await get_user({ username: 'admin' });
+    }
+}
+
+module.exports = {
+    DomainVerificationService,
+};

src/backend/src/modules/domain/TXTVerifyService.js

@@ -0,0 +1,21 @@
+const { get_user } = require("../../helpers");
+const BaseService = require("../../services/BaseService");
+
+class TXTVerifyService extends BaseService {
+    async _init () {
+        const require = this.require;
+        const dns = require('dns').promises;
+
+        const svc_event = this.services.get('event');
+        svc_event.on('domain.get-controlling-user', async (_, event) => {
+            let records = await dns.resolveTxt(`_puter-verify.${event.domain}`);
+            records = records.flat();
+        
+            console.log('got records :: ', records);
+        })
+    }
+}
+
+module.exports = {
+    TXTVerifyService,
+}