fix: postgres build plugin w --production (#1018)

as reported in the issue, with default `cds build --production` no
postgres build artifacts have been generated.

this was due to a misconfiguration in our `postgres/package.json`

---

```shell
cds init reproduce --add tiny-sample
cd reproduce
cds add postgres
```

you can now observe the malformed `cds env`

```shell
❯ cds env requires.db --profile production
{
  impl: '@cap-js/postgres',
  credentials: { url: 'db.sqlite' },
  kind: 'sqlite',
  dialect: 'postgres',
  vcap: { label: 'postgresql-db' },
  schema_evolution: 'auto'
}
```

and the broken build (missing postgres build task):

```
❯ cds build --production
building project [/Users/patricebender/SAPDevelop/dev/cds-dbs/postgres/test/tiny-sample], clean [true]
cds-dk [8.7.1], cds [8.8.0], compiler [5.7.5], home [/Users/patricebender/SAPDevelop/dev/cds]

{
  build: {
    target: 'gen',
    tasks: [
      { for: 'nodejs', src: 'srv', options: { model: ['db', 'srv'] }}
    ]
  }
}
```

.github/workflows/test.yml

@@ -32,6 +32,7 @@ jobs:
           cache: 'npm'
 
       - run: npm ci
+      - run: npm install -g @sap/cds-dk
       - run: npm run lint
       - id: hxe
         uses: ./.github/actions/hxe

postgres/package.json

@@ -59,7 +59,7 @@
         },
         "postgres": {
           "impl": "@cap-js/postgres",
-          "kind": "sqlite",
+          "kind": "postgres",
           "dialect": "postgres",
           "vcap": {
             "label": "postgresql-db"

postgres/test/cds-build.test.js

@@ -0,0 +1,30 @@
+'use strict'
+
+// make sure the build plugin works
+
+const path = require('path')
+const fs = require('fs')
+const { execSync } = require('child_process')
+const cds = require('../../test/cds.js')
+
+const workDir = path.join(__dirname, 'tiny-sample')
+const genDir = path.join(workDir, 'gen')
+const dbDest = path.join(genDir, 'pg/db')
+
+// delete the generated folder after each test
+afterEach(() => {
+  if (fs.existsSync(genDir)) fs.rmSync(genDir, { recursive: true })
+})
+
+describe('cds build plugin', () => {
+  const { expect } = cds.test
+  test('should run pg build with explicit build task', () => {
+    execSync('npx cds build --for postgres', { cwd: workDir })
+    expect(fs.existsSync(path.join(dbDest, 'csn.json'))).to.be.true
+  })
+
+  test('should run pg build with production profile', () => {
+    execSync('npx cds build --production', { cwd: workDir })
+    expect(fs.existsSync(path.join(dbDest, 'csn.json'))).to.be.true
+  })
+})

postgres/test/tiny-sample/db/data/my.bookshop-Books.csv

@@ -0,0 +1,3 @@
+ID,title,stock
+1,Wuthering Heights,100
+2,Jane Eyre,500

postgres/test/tiny-sample/db/schema.cds

@@ -0,0 +1,7 @@
+namespace my.bookshop;
+
+entity Books {
+  key ID : Integer;
+  title  : String;
+  stock  : Integer;
+}

postgres/test/tiny-sample/package.json

@@ -0,0 +1,8 @@
+{
+  "name": "tiny-sample",
+  "version": "1.0.0",
+  "description": "A simple CAP project, to test the build plugin",
+  "dependencies": {
+    "@cap-js/postgres": "../../."
+  }
+}

postgres/test/tiny-sample/srv/cat-service.cds

@@ -0,0 +1,5 @@
+using my.bookshop as my from '../db/schema';
+
+service CatalogService {
+    @readonly entity Books as projection on my.Books;
+}