[UDFs] support functions in python

[graciegoheen]

Housekeeping

• I am a maintainer of dbt-core

Short description

many warehouses support python function (snowflake docs)

this allows users to write functions beyond what SQL can do

Acceptance criteria

• i can create a function in python
• i can write python code for the logic of that function
• the function create statement will specify that the language is python

CREATE OR REPLACE FUNCTION addone(i INT)
  RETURNS INT
  LANGUAGE PYTHON
  RUNTIME_VERSION = '3.9'
  HANDLER = 'addone_py'
AS $$
def addone_py(i):
  return i+1
$$;