feat: add personal mentoring dates

[karlovich]

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🤔 This is a ...

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

🔗 Related issue link

#2586

💡 Background and solution

Two additional fields for

• UI changed
• DTOs changed
• Migration script added
• Backup sql updated
• Openapi updated

☑️ 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

[github-actions]

📦 Next.js Bundle Analysis

This analysis was generated by the next.js bundle analysis action 🤖

One Page Changed Size

The following page changed size from the code in this PR compared to its base branch:

Page	Size (compressed)	First Load	% of Budget (500 KB)
/admin/courses	399.37 KB	475.57 KB	95.11% (🟡 +0.03%)

Details

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[valerydluski]

lgtm

[karlovich]

@valerydluski could you pls re-review the PR, I did changes in export dto for having the dates in CDN/app/courses.json for using the mentoring dates in RS WEB site and also reset the personal mentoring start/end dates to null if personalMentoring is false for the data consistency. tested locally, no issues found. Changes for exporting to CDN could vefiry only at prod env after the merge.