Is it possible to create a custom validation for fields in configuration? (Stores > Settings > configuration)
I created a
system.xml file but the default values for the validate tag are not enough for my needs and I would like to create my own rules.
I found an other question about this but it doesn't say how and where I should put/declare the validation method.
Is this possible or is the only solution to create a backend model with a beforeSave function?