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/domain_moderator.go

@@ -0,0 +1,57 @@
+package main
+
+import (
+	"time"
+)
+
+type moderator struct {
+	Email   string    `json:"email"`
+	Domain  string    `json:"domain"`
+	AddDate time.Time `json:"addDate"`
+}
+
+func domainModeratorList(domain string) ([]moderator, error) {
+	statement := `
+		SELECT email, addDate
+		FROM moderators
+		WHERE domain=$1;
+	`
+	rows, err := db.Query(statement, domain)
+	if err != nil {
+		logger.Errorf("cannot get moderators: %v", err)
+		return nil, errorInternal
+	}
+	defer rows.Close()
+
+	moderators := []moderator{}
+	for rows.Next() {
+		m := moderator{}
+		if err = rows.Scan(&m.Email, &m.AddDate); err != nil {
+			logger.Errorf("cannot Scan moderator: %v", err)
+			return nil, errorInternal
+		}
+
+		moderators = append(moderators, m)
+	}
+
+	return moderators, nil
+}
+
+func isDomainModerator(domain string, email string) (bool, error) {
+	statement := `
+		SELECT EXISTS (
+			SELECT 1
+			FROM moderators
+			WHERE domain=$1 AND email=$2
+		);
+	`
+	row := db.QueryRow(statement, domain, email)
+
+	var exists bool
+	if err := row.Scan(&exists); err != nil {
+		logger.Errorf("cannot query if moderator: %v", err)
+		return false, errorInternal
+	}
+
+	return exists, nil
+}