feat: add new backend system support for existing backend plugins that have not been migrated over yet

[Zaperex]

Description

Adds new backend system support for the following backend plugins:

• 3scale-backend
• aap-backend
• keycloak-backend
• kiali-backend
• matomo-backend
• ocm-backend
• orchestrator-backend
• notifications-backend
• feedback-backend
• quay-actions
• kubernetes-actions
• regex-actions
• servicenow-actions
• sonarqube-actions

Update the templates for newly created plugins/modules in the janus-cli to support the new backend system.

Which issue(s) does this PR fix

Fixes #1062

How to test changes / Special notes to the reviewer

Build the plugins with export-dynamic and dynamically install them into this experimental branch of the showcase

New backend support for the rbac-backend plugin will be added in a separate PR.

Removed the src/dynamic/alpha.ts file for backend plugins that only export one module or plugin as it was deemed redundant with the presence of src/alpha.ts when running yarn export-dynamic with only one export.

[Zaperex]

Currently it seems the ocm-backend and the orchestrator-backend plugin are exporting both a plugin and a module, in this cases what would be the default export in src/alpha.ts?

Would we need to separate the ocm-backend plugin into 2 separate packages (one for the EntityProvider module and one for plugin providing the routes that the frontend communicates with?) and potentially a 3rd package for the extension points?

[Zaperex]

Trying to do an export * from './dynamic/alpha', similar to how the orchestrator does it, doesn't work.

Tested by installing the package in the new backend system:

backend.add(import('@janus-idp/backstage-plugin-orchestrator-backend/alpha'));

However, doing so would result in the following error:

backend:start: /home/frkong/coding/janus-idp/backstage-showcase/node_modules/@backstage/backend-app-api/src/wiring/BackendInitializer.ts:103
backend:start:       throw new Error(
backend:start:             ^
backend:start: 
backend:start: 
backend:start: Error: Failed to add feature, invalid type 'undefined'
backend:start:     at BackendInitializer.addFeature_fn (/home/frkong/coding/janus-idp/backstage-showcase/node_modules/@backstage/backend-app-api/src/wiring/BackendInitializer.ts:103:13)
backend:start:     at BackendInitializer.doStart_fn (/home/frkong/coding/janus-idp/backstage-showcase/node_modules/@backstage/backend-app-api/src/wiring/BackendInitializer.ts:155:7)
backend:start:     at BackendInitializer.start (/home/frkong/coding/janus-idp/backstage-showcase/node_modules/@backstage/backend-app-api/src/wiring/BackendInitializer.ts:148:5)
backend:start:     at BackstageBackend.start (/home/frkong/coding/janus-idp/backstage-showcase/node_modules/@backstage/backend-app-api/src/wiring/BackstageBackend.ts:42:11)
backend:start: 
backend:start: Node.js v18.18.0

Printing out the module that is returned from the import with

import('@janus-idp/backstage-plugin-orchestrator-backend/alpha')
  .then(module => {
    console.log(module);
  })
  .catch(error => {
    console.error('Error importing module:', error);
  });

yields:

backend:start: [Module: null prototype] {
backend:start:   __esModule: true,
backend:start:   default: {
backend:start:     dynamicPluginInstaller: { kind: 'new', install: [Function: install] }
backend:start:   },
backend:start:   dynamicPluginInstaller: { kind: 'new', install: [Function: install] }
backend:start: }

which does not match the expected input types for the BackstageBackend.add() function.

A package that does properly support the new backend system like @backstage/plugin-events-backend/alpha would print out the following:

backend:start: [Module: null prototype] {
backend:start:   __esModule: true,
backend:start:   default: {
backend:start:     default: [Function: factory] { '$$type': '@backstage/BackendFeatureFactory' }
backend:start:   }
backend:start: }

[Zaperex]

If I exported the module and plugin individually in the src/alpha.ts, like follows:

export { catalogModuleOCMEntityProvider } from './providers';
export { ocmPlugin } from './service/router';

Then I was able to import the modules properly, if I explicitly imported them in a .then() . However, I had to wrap everything in an async main function to put an await on the import. Otherwise, the backend will start before the modules are imported.
ex:

async function main() {
  const backend = createBackend();
  // Insert other backend.add(...) statements here
  await import('@zaperex-org/backstage-plugin-ocm-backend')
    .then(module => {
      backend.add(module.catalogModuleOCMEntityProvider);
      backend.add(module.ocmPlugin);
    })
    .catch(error => {
      console.error('Error importing module:', error);
    });
  backend.start();
}

main().catch(error => {
  console.error('Backend failed to start up', error);
  process.exit(1);
});

Not sure if this would be ideal as it would change the default backend index.ts structure for the new backend.

[Zaperex]

If we export all the modules/plugins, then the users can alternatively just not use the dynamic package import and install the ocm-backend plugin package statically like in the following example:

import { catalogModuleOCMEntityProvider, ocmPlugin } from '@zaperex-org/backstage-plugin-ocm-backend';

const backend = createBackend();
 // Insert other backend.add(...) statements here
backend.add(catalogModuleOCMEntityProvider);
backend.add(ocmPlugin);

backend.start();