feature - Add identity resolution

[awoehrl]

It would be great to have an identity resolution logic in the package. This would consist of multiple steps:

1. Have a stitching table that combines the user identifiers
   Depending on the use case this could be a table defined in dbt or in a more complex case a python implementation or a graph database.

Example code

--- user_identity_mapping.sql

select distinct
  anonymous_customer_id,
  last_value(customer_id) over(
    partition by anonymous_customer_id
    order by event_tstamp
    rows between unbounded preceding and unbounded following
  ) as customer_id,
  max(event_tstamp) over (partition by anonymous_customer_id) as end_tstamp

from events

where customer_id is not null
and anonymous_customer_id is not null

2. Update the activities via a post hook
   With that table we could implement a post hook that updates the customer_id as well as the activity_occurence and activity_repeated_at fields.

Example code for the customer_id update

      update activity as a
      set a.customer_id = ui.customer_id
      from user_identity_mapping as ui
      where a.anonymous_customer_id = ui.anonymous_customer_id;

Alternatives to consider:

• Is it really neccessary to have two id columns in activities?

[bcodell]

Possible implementations:

• explicit/manual recursion (see rudderlabs/dbt-id-stitching)
• recursive query (see dbt-graph-theory)
• python dataproc/snowpark
• python via duckdb process