chore: Wrap membership event reasons in parentheses - #1470

Description

This PR attempts to slightly improve the visualization of membership join events.

Before

Without the PR, membership events' change reasons are either blended with the rest of the service message text, or not shown entirely in the case of join reasons.

After

With the PR, all reasons are displayed, and they are wrapped in parentheses.

Type of change

• Bug fix (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)
• This change requires a documentation update

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
• My changes generate no new warnings

AI disclosure:

• Partially AI assisted (clarify which code was AI assisted and briefly explain what it does).
• Fully AI generated (explain what all the generated code does in moderate detail).