Add support for Fusion

[b-per]

This is a draft PR for supporting Fusion.

Integration tests are not passing so I will need to investigate, but creating a branch and draft PR to start the work on getting the package compatible with Fusion.

This is not ready to be merged yet but people willing to give this update a go can install the package using the git method:

  - git: "https://github.com/b-per/dbt-snowplow-utils.git"
    revision: "update-fusion"

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