* callback plugins: use f-strings
* add changelog frag
* manual change for few occurrences
* manual change for few occurrences
* adjustment from review
* adjustment from review
* adjustment from review
* Update plugins/callback/splunk.py
Co-authored-by: Felix Fontein <felix@fontein.de>
* replace str templating with JSON templating
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Co-authored-by: Felix Fontein <felix@fontein.de>