Add support for snowflake roles

[thomas-brx]

This PR adds support for configuring the role to assume in SnowFlake.
If not set, "role" will simply not be added to the generated configuration file, so it should be backwards compatible.

[snowplowcla]

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[thomas-brx]

Signed:

…

On 2 Aug 2023, at 12:18, Snowplow CLA bot ***@***.***> wrote: Thanks for your pull request. Is this your first contribution to a Snowplow open source project? Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA). 📝 Please visit https://docs.snowplowanalytics.com/docs/contributing/contributor-license-agreement/ <https://docs.snowplowanalytics.com/docs/contributing/contributor-license-agreement/> to learn more and sign. Once you've signed, please reply here (e.g. I signed it!) and we'll verify. Thanks. — Reply to this email directly, view it on GitHub <#19 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AACYK4D4T7EXR5DRGRUMCI3XTISNTANCNFSM6AAAAAA3BBJE3E>. You are receiving this because you authored the thread.

[snowplowcla]

Confirmed! @thomas-brx has signed the Contributor License Agreement. Thanks so much.