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/commenter_test.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+	"testing"
+)
+
+func TestCommenterIsProviderUserBasics(t *testing.T) {
+	failTestOnError(t, setupTestEnv())
+
+	commenterNew("test@example.com", "Test", "undefined", "https://example.com/photo.jpg", "google")
+
+	exists, err := commenterIsProviderUser("google", "test@example.com")
+	if err != nil {
+		t.Errorf("unexpected error checking if commenter is a provider user: %v", err)
+		return
+	}
+
+	if !exists {
+		t.Errorf("user expected to exist not found")
+		return
+	}
+
+	exists, err = commenterIsProviderUser("google", "test2@example.com")
+	if err != nil {
+		t.Errorf("unexpected error checking if commenter is a provider user: %v", err)
+		return
+	}
+
+	if exists {
+		t.Errorf("user expected to not exist not found")
+		return
+	}
+}
+
+func TestCommenterIsProviderUserEmpty(t *testing.T) {
+	failTestOnError(t, setupTestEnv())
+
+	if _, err := commenterIsProviderUser("google", ""); err == nil {
+		t.Errorf("expected error not found when checking for user with empty email")
+		return
+	}
+}