ci: test basic application response of the docker build

Note by muxator:
This commit introduced a copied & modified version of the testing files
loadSettings.js and pad.js.

It's Christmas night, and we want to shipt this feature, so I merged it anyway,
adding a note in both the original and copied files so that hopefully someone
in the distant future is going to merge them back again.

tests/container/specs/api/pad.js

@@ -0,0 +1,38 @@
+/*
+ * ACHTUNG: this file was copied & modified from the analogous
+ * <basedir>/tests/backend/specs/api/pad.js
+ *
+ * TODO: unify those two files, and merge in a single one.
+ */
+
+const supertest = require(__dirname+'/../../../../src/node_modules/supertest');
+const settings = require(__dirname+'/../../loadSettings').loadSettings();
+const api = supertest('http://'+settings.ip+":"+settings.port);
+
+var apiVersion = 1;
+
+describe('Connectivity', function(){
+  it('can connect', function(done) {
+    api.get('/api/')
+    .expect('Content-Type', /json/)
+    .expect(200, done)
+  });
+})
+
+describe('API Versioning', function(){
+  it('finds the version tag', function(done) {
+    api.get('/api/')
+    .expect(function(res){
+      if (!res.body.currentVersion) throw new Error("No version set in API");
+      return;
+    })
+    .expect(200, done)
+  });
+})
+
+describe('Permission', function(){
+  it('errors with invalid APIKey', function(done) {
+    api.get('/api/'+apiVersion+'/createPad?apikey=wrong_password&padID=test')
+    .expect(401, done)
+  });
+})