Implement custom prefixes

[No767]

Summary

This PR aims to add custom prefixes for Rodhaj. As Modmail already supports this feature, and having custom prefixes is best practice, Rodhaj will get them and follow suit. The custom prefix implementation is based off of Kumiko's implementation

Types of changes

What types of changes does your code introduce to Rodhaj
Put an x in the boxes that apply

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (Updates to README.md, the documentation, etc)
• Other (if none of the other choices apply)

Checklist

Put an x in the boxes that apply

• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes. (if appropriate)
• All workflows (except pre-commit.ci) pass with my new changes
• This PR does not address a duplicate issue or PR

[sonarcloud]

Quality Gate passed

Kudos, no new issues were introduced!

0 New issues
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud