'Post request to get specific number of users from Synapse..
This need a user have a administrator access in Synapse.
Example:
http://localhost:8008/_matrix/client/api/v1/admin/users_paginate/
@admin:user?access_token=admin_access_token
JsonBodyToSend:
"start": "0",
"limit": "10
Returns:
200 OK with json object {list[dict[str, Any]], count} or empty object.'

@defer.inlineCallbacks
def on_POST(self, request, target_user_id):

    UserID.from_string(target_user_id)
    requester = (yield self.auth.get_user_by_req(request))
    is_admin = (yield self.auth.is_server_admin(requester.user))
    if (not is_admin):
        raise AuthError(403, 'You    are    not    a    server    admin')
    order = 'name'
    params = parse_json_object_from_request(request)
    limit = params['limit']
    start = params['start']
    if (not limit):
        raise SynapseError(400, "Missing    'limit'    arg")
    if (not start):
        raise SynapseError(400, "Missing    'start'    arg")
    logger.info('limit:    %s,    start:    %s', limit, start)
    ret = (yield self.handlers.admin_handler.get_users_paginate(order, start, limit))
    defer.returnValue((200, ret))
