code: @Override
      public AddRoleToDBInstanceResult addRoleToDBInstance(AddRoleToDBInstanceRequest request) {
          request = beforeClientExecution(request);
          return executeAddRoleToDBInstance(request);
      }
docs: <p>
  Associates an AWS Identity and Access Management (IAM) role with a DB instance.
  </p>
  <note>
  <p>
  To add a role to a DB instance, the status of the DB instance must be <code>available</code>.
  </p>
  </note>
  
  @param addRoleToDBInstanceRequest
  @return Result of the AddRoleToDBInstance operation returned by the service.
  @throws DBInstanceNotFoundException
  <i>DBInstanceIdentifier</i> doesn't refer to an existing DB instance.
  @throws DBInstanceRoleAlreadyExistsException
  The specified <i>RoleArn</i> or <i>FeatureName</i> value is already associated with the DB instance.
  @throws InvalidDBInstanceStateException
  The DB instance isn't in a valid state.
  @throws DBInstanceRoleQuotaExceededException
  You can't associate any more AWS Identity and Access Management (IAM) roles with the DB instance because
  the quota has been reached.
  @sample AmazonRDS.AddRoleToDBInstance
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/rds-2014-10-31/AddRoleToDBInstance" target="_top">AWS API
  Documentation</a>