## What does this PR do?
- Adds AB tests middleware that redirects users to the app-dir pages with probability that is defined by env var
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Fixes # (issue)
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## Requirement/Documentation
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This PR requires new env variables:
`APP_ROUTER_EVENT_TYPES_ENABLED` - boolean that defines if app dir event-types page redirect is enabled
`AB_TEST_BUCKET_PROBABILITY` - number [0, 100] that defines the percentage of users getting redirected to the app dir pages
## Type of change
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- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] Chore (refactoring code, technical debt, workflow improvements)
- [ ] 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
## How should this be tested?
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Does not requires testing, implements middleware as a dead code
## Mandatory Tasks
- [x] Make sure you have self-reviewed the code. A decent size PR without self-review might be rejected.
