feat(blob): add support unique transaction for get blob

[jesusvilla]

For unique transaction:

const Firebird = require('node-firebird');

async function query (sql, bindings = []) {
  return new Promise((resolve, reject) => {
    Firebird.attach(config, (error, conn) => {
      if (error) {
        return reject(error);
      }

      conn.transaction(Firebird.ISOLATION_READ_COMMITED, (err, transaction) => {
        if (error) {
          return reject(error);
        }
        transaction.query(sql, bindings, (error, result) => {
          if (error) {
            transaction.rollback();
            return reject(error);
          }

          const arrBlob = [];
          for (const item of result) {
            const fields = Object.keys(item);
            for (const key of fields) {
              if (typeof item[key] === 'function') {
                item[key] = new Promise((resolve, reject) => {
                  // the same transaction is used (better performance)
                  // this is optional
                  item[key](transaction, (error, name, event, row) => {
                    if (error) {
                      return reject(error);
                    }

                    let value = '';
                    event.on('data', (chunk) => {
                      value += chunk.toString('binary');
                    });
                    event.on('end', () => {
                      resolve({ value, column: name, row });
                    });
                  });
                });
                arrBlob.push(item[key]);
              }
            }
          }

          Promise.all(arrBlob).then((blobs) => {
            for (const blob of blobs) {
              result[blob.row][blob.column] = blob.value;
            }

            transaction.commit((error) => {
              if (error) {
                transaction.rollback();
                return reject(error);
              }
  
              conn.detach();
              resolve(result);
            }).catch((error) => {
              transaction.rollback();
              reject(error);
            });
          })
        });
      });
    });
  });
}