[api] Stop observation to address

[olemis]

[DELETE] /api/transactions/history/to/{address}/observation

Should stop observation of the transactions that transfer fund to the address . Should affect result of the [GET] /api/transactions/history/to/{address} .

Errors:

* `204 No content` : transactions to the  address  are not observed.

Python implementation

@api.route('/transactions/history/to/<string:address>/observation', methods=['DELETE'])
def del_history_to_address(address):
    """
    Stops observation of the transactions that transfer fund to the address 
    """
    
    result = delete_transaction_observation_to_address(address)

    # if successfully deleted from observation list, return a plain 200
    if "error" in result:
        return make_response(jsonify(build_error(result["error"])), result["status"])
    else:
        return ""