By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Description

• removed Python 3.7 and raised the minimum version needed to 3.8
• replaced deep_merge package with an optimized copy of it, because it is not maintained for quite some time

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my feature, policy, or fix is effective and works
• New and existing tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules