refactor: add self transaction to activity directions

[MarkNerdi996]

Summary

Add SelfTransaction as an ActivityDirection because everything gets more readable and explicit

Changelog

- Add `SelfTransaction` as an `ActivityDirection` 

Relevant Issues

Closes #4979

Testing

Platforms

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• Desktop
  • MacOS
  • Linux
  • Windows
• Mobile
  • iOS
  • Android

Instructions

Please describe the specific instructions, configurations, and/or test cases necessary to test and verify that your changes work as intended.

...

Checklist

Please tick all of the following boxes that are relevant to your changes.

• I have followed the contribution guidelines for 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 added or modified tests that prove my changes work as intended
• I have verified that new and existing unit tests pass locally with my changes
• I have verified that my latest changes pass CI workflows for testing and linting
• I have made corresponding changes to the documentation

[nicole-obrien]

Some small changes

[nicole-obrien]

LGTM!