BULL-3221: express mvp

• added unit tests, note that the dataLayer unit tests are also overwritten when dataLayer is replaced by a real implementation
• added production dockerfile

src/data/dataLayer.spec.js

+const { getDbVersion, healthCheck, runMigrations } = require('../data/dataLayer');
+
+describe('Data', () => {
+    describe('runMigrations', () => {
+        it('is a stub', async () => {
+            await runMigrations();
+        });
+    });
+    describe('healthCheck', () => {
+        it('returns the stubbed out data', async () => {
+            const result = await healthCheck();
+            expect(result).toEqual({
+                healthy: true,
+                message: "Health check succeeded, but no database is deployed"
+            });
+        });
+    });
+    describe('getDbVersion', () => {
+        it('returns the stubbed out data', async () => {
+            const result = await getDbVersion();
+            expect(result).toEqual("no database deployed");
+        });
+    });
+});
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