added fk methods to TableBuilder

db/migrations/builder/TableBuilder.h

@@ -60,6 +60,16 @@ namespace db {
           return *this;
         }
 
+        CreateTableBuilder &fk(const std::string &key, const std::string &reference_table, const std::string &foreign_key, const std::string &opts = "") {
+          m_table.body += "\tFOREIGN KEY (" + key + ") REFERENCES " + reference_table + "(" + foreign_key + ")" + opts + ",\n";
+          return *this;
+        }
+
+        CreateTableBuilder &constraint(const std::string &name, const std::string &opts) {
+          m_table.body += "\tCONSTRAINT " + name + " UNIQUE (" + opts + "),\n";
+          return *this;
+        }
+
         CreateTableBuilder &close() {
           m_table.body.pop_back();
           m_table.body.pop_back();