fix: dateadd supports more than 25 days for every unit of time (DNA-21769: DNA-21829)

[cverhoef]

Description

• To fix the bug: the number argument is casted to a bigint for Databricks. Only for Databricks we do computations on this argument which can result in (negative) overflow values when the number is of type int instead of bigint.
• Simplified the implementation:
  • Replaced the date_add used for day and week with the same approach as for the more granular units. We now have 2 different approaches instead of 3 to cover all scenarios.
  • Moved the "Jinja set variables" to places more close to where it is used.
• Docs: updated the readme to fix the table of contents and removed the condition that the number of units should be an integer.
• Added tests:
  • Additions of more than 25 days. Both in seconds, which we use ourselves, but also in days as this seems to be a more standard scenario.
  • Additions of doubles. This is also supported and used, although the values differ per database as doubles are rounded differently.

Release

• Direct release (main)
• Merge to dev (or other) branch
  • Why:

Did you consider?

• Does it Work on Automation Suite / SQL Server
• Does it Work on Automation Cloud / Snowflake
• What is the performance impact?
• The version number in dbt_project.yml