Issue Summary
Some actions are failing to send because Alerta can't decode sent information.

Environment

• OS: Linux

• Deployment: Docker 5.0.1

• Database: Mysql

To Reproduce
Steps to reproduce the behavior:

1. Go to 'Zabbix 5.0'
2. Create a host with temperature discovery with °C or use of none English characters.
3. Configure the standard action template and start an alert. You can see that "value -> 61 \udcc2\udcb0C" displayed on error message in Zabbix 5.0
4. See error (include command output)

Action Template:
resource={HOST.NAME1}
event={ITEM.KEY1}
environment=Production
severity={TRIGGER.SEVERITY}
status={TRIGGER.STATUS}
ack={EVENT.ACK.STATUS}
service=
customer={$TENANT}
attributes.customer={$TENANT}
group={TRIGGER.HOSTGROUP.NAME}
value={ITEM.VALUE1}
text={TRIGGER.STATUS}: {TRIGGER.NAME}
tags={EVENT.TAGS}
attributes.ip={HOST.IP1}
attributes.thresholdInfo={TRIGGER.TEMPLATE.NAME}: {TRIGGER.EXPRESSION}
dateTime={EVENT.DATE}T{EVENT.TIME}Z
type=zabbixAlert
attributes.zabbixUrl=http://\{$TENANT}-zabbix-web:8080
attributes.eventId={EVENT.ID}
attributes.triggerId={TRIGGER.ID}

Expected behavior
To be able to decode or accept with errors. The are no problems with Zabbix 4.0.