<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def add_authorization_policy(access_token, ck_id, oid):
    '''Add Media Service Authorization Policy.

    Args:
        access_token (str): A valid Azure authentication token.
        ck_id (str): A Media Service Asset Content Key ID.
        options_id (str): A Media Service OID.

    Returns:
        HTTP response. JSON body.
    '''
    path = '/ContentKeys'
    body = '{"AuthorizationPolicyId":"' + oid + '"}'
    return helper_add(access_token, ck_id, path, body)