Add suppliers notes app

notes/srv/external/data/API_BUSINESS_PARTNER-A_BusinessPartner.csv

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+BusinessPartner;BusinessPartnerFullName;BusinessPartnerType
+11;Alice Wonder;CUSTOMER;
+9980000082;Hugo Hollandaise;CUSTOMER

notes/srv/notes-service.cds

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+using sap.capire.notes from '../db/data-model';
+using { Suppliers as MashupSuppliers } from '../db/mashup';
+using { API_BUSINESS_PARTNER as BusinessPartner } from './external/API_BUSINESS_PARTNER.csn';
+
+/**
+ * Notes Service
+ *
+ * Maintain notes for suppliers
+ */
+service NotesService {
+    entity Notes as projection on notes.Notes;
+    entity Suppliers as projection on MashupSuppliers;
+}

notes/srv/notes-service.js

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+const cds = require("@sap/cds");
+
+const s4apiKey = process.env.S4_APIKEY;
+if (!s4apiKey && cds.env.profiles.indexOf("sandbox") >= 0) {
+  console.error(
+    "[ERROR] Provide API Key in env var S4_APIKEY for S/4 Sandbox: https://api.sap.com/api/API_BUSINESS_PARTNER/resource -> Show API Key"
+  );
+  process.exit(1);
+}
+
+module.exports = cds.service.impl(async function () {
+  const { Notes, Suppliers } = this.entities;
+
+  const bpService = await cds.connect.to("API_BUSINESS_PARTNER");
+
+  // REVISIT: This is a workaround for the missing capability to add headers to the service
+  const bpServiceDelegate = {
+    run: query => bpService.send({ query, headers: { APIKey: s4apiKey } })
+  };
+
+  // Suppliers?$expand=notes
+  this.on("READ", Suppliers, async (req, next) => {
+    const expandIndex = req.query.SELECT.columns.findIndex(
+      ({ expand, ref }) => expand && ref[0] === "notes"
+    );
+    if (expandIndex < 0) return next();
+
+    req.query.SELECT.columns.splice(expandIndex, 1);
+    if (!req.query.SELECT.columns.find(
+            column => column.ref.find((ref) => ref == "ID"))
+       )
+      req.query.SELECT.columns.push({ ref: ["ID"] });
+
+    const suppliers = await next();
+
+    // Request all associated notes
+    const supplierIds = suppliers.map((supplier) => supplier.ID);
+    const notes = await this.run(SELECT.from(Notes).where({ supplier_ID: supplierIds }));
+
+    // Convert in a map for easier lookup
+    const notesForSuppliers = {};
+    for (const note of notes) {
+      if (!notesForSuppliers[note.supplier_ID]) notesForSuppliers[note.supplier_ID] = [];
+      notesForSuppliers[note.supplier_ID].push(note);
+    }
+
+    // Add notes to result
+    for (const supplier of suppliers) {
+      const notesForSupplier = notesForSuppliers[supplier.ID];
+      if (notesForSupplier) supplier.notes = notesForSupplier;
+    }
+
+    return suppliers;
+  });
+
+
+  this.on("READ", Suppliers, async req => {
+    return bpServiceDelegate.run(req.query);
+  });
+
+});