Adding test queries for Sankey download

[kaskranenburgQ]

This PR adds test queries for the Sankey download.
The logic behind the tests is that for each carrier in the Sankey download:
Conversion Output + Primary Demand Output = Conversion Input + Final demand Input + Losses*

*The losses that are taken into account are conversion losses to the same carrier, i.e. electricity to electricity conversion losses.

With the rake task, the queries that are given for each group are extracted from the sankey_csv.yml and summed up in a dedicated query for each of the categories.

Since only one type of losses is taken into account, these queries are not taken into account in the tests.

Goes together with PR 178 from mechanical_turk

[github-actions]

This pull request has had no activity for 60 days and will be closed in 7 days. Removing the "Stale" label or posting a comment will prevent it from being closed automatically. You can also add the "Pinned" label to ensure it isn't marked as stale in the future.

[github-actions]

This pull request has had no activity for 60 days and will be closed in 7 days. Removing the "Stale" label or posting a comment will prevent it from being closed automatically. You can also add the "Pinned" label to ensure it isn't marked as stale in the future.

[github-actions]

This pull request has had no activity for 60 days and will be closed in 7 days. Removing the "Stale" label or posting a comment will prevent it from being closed automatically. You can also add the "Pinned" label to ensure it isn't marked as stale in the future.