Converting variable names to lower_case_underscore style

[ggrell]

In our JSON structures, we generally name fields similarly to the JSON data field name counterparts. When generating JSON mapping code, it would be nice to be able to directly map from someFieldName to some_field_name. I see that Stencil has capitalize, uppercase & lowercase, and Sourcery additionally provides upperFirst (via what looks like a Stencil custom filter).

I'm interested in contributing a lowercaseUnderscore filter if that's something that people would find valuable.

[krzysztofzablocki]

We also use https://github.com/SwiftGen/StencilSwiftKit which has few other filters like snakeToCamelCase / snakeToCamelCaseNoPrefix, I think that might actually cover this already?

[ggrell]

Woah, I didn't know StencilSwiftKit had additional filters added to it! Looks like snakecase hasn't been exposed as a filter, happy to take care of it if needed.

[krzysztofzablocki]

sounds great, but we should do it on the StencilSwiftKit repo 👍