feat(course-users): add activist role

[ThorsAngerVaNeT]

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🤔 This is a ...

• New feature
• Bug fix
• Performance optimization
• Refactoring
• Test Case
• Documentation update
• Other

🔗 Related issue link

We have an activist field in the user table that is not used and can't be updated anyhow in UI. This field could be used for more convenient filtering in Heroes Radar.

💡 Background and solution

Added Activist role in Course Users. That way we could have data on which course students became activists and update the activist field in the user table.
The Activist role doesn't yet have any additional access on courses.

☑️ Self Check before Merge

⚠️ Please check all items below before review. ⚠️

• Database migration is added or not needed
• Documentation is updated/provided or not needed
• Changes are tested locally

[apalchys]

@valerydluski please review

[valerydluski]

@apalchys approved