api: Add go files

I know this is a huge commit, but I can't be bothered to check
this in part by part.

api/oauth_google_test.go

@@ -0,0 +1,59 @@
+package main
+
+import (
+	"os"
+	"testing"
+)
+
+func resetGoogleVars() {
+	for _, env := range []string{"GOOGLE_KEY", "GOOGLE_SECRET"} {
+		os.Setenv(env, "")
+	}
+}
+
+func TestGoogleOauthConfigureBasics(t *testing.T) {
+	resetGoogleVars()
+
+	os.Setenv("GOOGLE_KEY", "google-key")
+	os.Setenv("GOOGLE_SECRET", "google-secret")
+
+	if err := googleOauthConfigure(); err != nil {
+		t.Errorf("unexpected error configuring google oauth: %v", err)
+		return
+	}
+
+	if googleConfig == nil {
+		t.Errorf("expected googleConfig!=nil got googleConfig=nil")
+		return
+	}
+}
+
+func TestGoogleOauthConfigureEmpty(t *testing.T) {
+	resetGoogleVars()
+
+	os.Setenv("GOOGLE_KEY", "google-key")
+
+	if err := googleOauthConfigure(); err == nil {
+		t.Errorf("expected error not found when configuring google oauth with empty GOOGLE_SECRET")
+		return
+	}
+
+	if googleConfig != nil {
+		t.Errorf("expected googleConfig=nil got googleConfig=%v", googleConfig)
+		return
+	}
+}
+
+func TestGoogleOauthConfigureEmpty2(t *testing.T) {
+	resetGoogleVars()
+
+	if err := googleOauthConfigure(); err != nil {
+		t.Errorf("unexpected error configuring google oauth with empty everything: should be disabled")
+		return
+	}
+
+	if googleConfig != nil {
+		t.Errorf("expected googleConfig=nil got googleConfig=%v", googleConfig)
+		return
+	}
+}