fix: properly cleanup related data when deleting connections

[andibeuge]

• Fix DeleteConnection function to properly cleanup environment variables, plugin connections, and connection tags associations
• Use database transaction to ensure atomicity of deletion operations
• Add comprehensive test coverage for the DeleteConnection function
• Environment variables were previously left orphaned in the database
• Plugin connections were not being cleaned up
• Connection tags associations were not being removed
• Guard rail rules connections are automatically cleaned up via CASCADE constraint

This fixes the bug where deleting a connection would leave related data orphaned in the database.

📝 Description

There seems to be a bug on deletion of connections - the env_vars remain in the database.

🔗 Related Issue

Fixes #

🚀 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)
• 📚 Documentation update
• 🎨 Style/UI update
• ♻️ Code refactor
• ⚡ Performance improvement
• ✅ Test update
• 🔧 Build configuration change
• 🧹 Chore

📋 Changes Made

• added programmatic removal of dependent entities on connection deletion

🧪 Testing

Tests updated

[github-actions]

All contributors have signed the CLA ✍️ ✅
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[andibeuge]

I have read the CLA Document and I hereby sign the CLA

[andibeuge]

recheck

[mtmr0x]

hi @andibeuge, Mat from hoop here.

Thanks for your contribution. Right now we have some design updates in parts related to your PR, so we will take this to a discussion inside, and we might hold this here for some weeks until we put all pieces together. Once we have everything sorted out, someone from the team will review this. If everything is in order, we will prepare the merge.

[andibeuge]

I have read the CLA Document and I hereby sign the CLA