Support CustomFucnctions #154
Description
Add support for code completion and inspection of user-implemented custom functions.
Available custom functions are the public methods on classes that implement the ExpressionFunctions interface. In Doma, such classes are registered via processor settings; in Doma Tools, we’ll provide a dedicated settings screen where users can configure and select the custom functions they wish to use.
https://doma.readthedocs.io/en/latest/expression/#using-custom-functions