Drop Python 3.6 Support

[VKTB]

Description:
The support for Python 3.6 ended at the end of 2021. Supporting this version of Python is an issue as there are so many dependencies that need upgrading but we cannot upgrade them as future versions drop 3.6 support. We are running 3.6 in production which is the main reason we have waited this long.

Acceptance criteria:

• Make the project work with Python 3.7 as the minimum version and update dependencies (including vulnerable ones where possible) accordingly
• Update any code that was added as a workaround for Python 3.6 to work with Python 3,7
• All CI checks pass