Escape variable names containing special characters for formulas

Adds backticks around names that contain anything other than `[A-Za-z0-9._]`. Centralises the helper that previously lived in multiple `.b.R` files so the implementation stays in one place.

Usage

.escapeVariableNames(var_names)

Arguments

var_names

Character vector of variable names.

Value

Character vector with non-syntactic names backtick-quoted.