Function append_to_query_with_separator 

pub fn append_to_query_with_separator<C: Conventions>(
    input: TokenStream,
) -> TokenStream

#[derive(AppendToQueryWithSeparator)]: the append to query with separator trait for a filter-options wrapper.

#[append_to_query(columns = Entity)] names the entity (deriving Columns) whose columns store the filtered domain fields.

Attributes: append_to_query (columns).