Ensure payload contains escaped double quotes

[rd-goran-pulevic]

Zabbix trigger elements, containing double quotes in definition
fields, are not being properly escaped when constructing JSON
payload. That, of course, breaks JSON standard.

Fix implements additional step, which deconstructs raw JSON payload
and, as an output, produces a valid JSON.

[BirolYildiz]

Hey @rd-goran-pulevic,
thanks for your PR. Do you have a sample .ilert file, generated by Zabbix, so we can reproduce this properly?
Thanks,
B.

[rd-goran-pulevic]

Some history - this is the error message:
ilert-zabbix.py: error: payload must be valid json (see https://support.ilert.de/display/ID/Zabbix+Integration). Error: Invalid control character at: line 7 column 35 (char 226)

Sample invalid payload:

{
    "EVENT.ID": "2468041",
    "HOST.HOST": "rs-int-front-001",
    "HOST.IP": "172.30.122.61",
    "TRIGGER.DESCRIPTION": "Traefik: ping API did not respond with OK",
    "TRIGGER.ID": "22342",
    "TRIGGER.NAME": "Traefik "live" signal missing / ping not OK",
    "TRIGGER.SEVERITY": "Average",
    "TRIGGER.STATUS": "PROBLEM",
    "TRIGGER.URL": "",
    "TRIGGER.VALUE": "1",
    "PLUGIN_VERSION": "1.0"
}
``

[rd-goran-pulevic]

labeled wontfix.

[yacut]

@rd-goran-pulevic If you are using Zabbix 4.4+, please try our native integration to solve the problem: https://docs.ilert.com/integrations/zabbix/native