Restructure project

We previously didn't really had any structure in our project apart
from creating a new folder for each package in our project root.
Now that we have accumulated some packages, we use the well-known
Golang project layout in order to clearly communicate our intent
with packages. See https://github.com/golang-standards/project-layout

internal/api/api_test.go

@@ -0,0 +1,70 @@
+package api
+
+import (
+	"github.com/gorilla/mux"
+	"github.com/stretchr/testify/assert"
+	"gitlab.hpi.de/codeocean/codemoon/poseidon/internal/config"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func mockHTTPHandler(writer http.ResponseWriter, _ *http.Request) {
+	writer.WriteHeader(http.StatusOK)
+}
+
+func TestNewRouterV1WithAuthenticationDisabled(t *testing.T) {
+	config.Config.Server.Token = ""
+	router := mux.NewRouter()
+	configureV1Router(router, nil, nil)
+
+	t.Run("health route is accessible", func(t *testing.T) {
+		request, err := http.NewRequest(http.MethodGet, "/api/v1/health", nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+		recorder := httptest.NewRecorder()
+		router.ServeHTTP(recorder, request)
+		assert.Equal(t, http.StatusNoContent, recorder.Code)
+	})
+
+	t.Run("added route is accessible", func(t *testing.T) {
+		router.HandleFunc("/api/v1/test", mockHTTPHandler)
+		request, err := http.NewRequest(http.MethodGet, "/api/v1/test", nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+		recorder := httptest.NewRecorder()
+		router.ServeHTTP(recorder, request)
+		assert.Equal(t, http.StatusOK, recorder.Code)
+	})
+}
+
+func TestNewRouterV1WithAuthenticationEnabled(t *testing.T) {
+	config.Config.Server.Token = "TestToken"
+	router := mux.NewRouter()
+	configureV1Router(router, nil, nil)
+
+	t.Run("health route is accessible", func(t *testing.T) {
+		request, err := http.NewRequest(http.MethodGet, "/api/v1/health", nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+		recorder := httptest.NewRecorder()
+		router.ServeHTTP(recorder, request)
+		assert.Equal(t, http.StatusNoContent, recorder.Code)
+	})
+
+	t.Run("protected route is not accessible", func(t *testing.T) {
+		// request an available API route that should be guarded by authentication.
+		// (which one, in particular, does not matter here)
+		request, err := http.NewRequest(http.MethodPost, "/api/v1/runners", nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+		recorder := httptest.NewRecorder()
+		router.ServeHTTP(recorder, request)
+		assert.Equal(t, http.StatusUnauthorized, recorder.Code)
+	})
+	config.Config.Server.Token = ""
+}