WIP: POC for template transformer funcs

[agedemenli]

Just a poc for #544

tested with:

  transformations:
    validation_mode: relaxed
    table_transformers:
      - schema: public
        table: test
        column_transformers:
          name:
            name: template
            parameters:
              template: >
                {{- my_name_tr .GetValue -}}
              functions:
                - template_function_name: my_name_tr
                  name: greenmask_firstname
                  parameters:
                    gender: Male