ActiveRecord::RecordNotUnique: Mysql2::Error: Duplicate entry 'github-39134240' for key 'users.index_users_on_provider_and_uid' (ActiveRecord::RecordNotUnique)

## Error

```
Duplicate entry 'github-28079255' for key 'users.index_users_on_provider_and_uid' (Mysql2::Error)
```

## Stack trace

```
mysql2/client.rb:151 in _query
mysql2/client.rb:151 in block in Mysql2::Client#query
mysql2/client.rb:150 in Thread.handle_interrupt
mysql2/client.rb:150 in query
active_record/connection_adapters/mysql2/database_statements.rb:100 in block (2 levels) in ActiveRecord::ConnectionAdapters::Mysql2::DatabaseStatements#raw_execute
active_record/connection_adapters/abstract_adapter.rb:1027 in block in ActiveRecord::ConnectionAdapters::AbstractAdapter#with_raw_connection
active_support/concurrency/null_lock.rb:9 in synchronize
active_record/connection_adapters/abstract_adapter.rb:999 in with_raw_connection
active_record/connection_adapters/mysql2/database_statements.rb:98 in block in ActiveRecord::ConnectionAdapters::Mysql2::DatabaseStatements#raw_execute
active_support/notifications/instrumenter.rb:58 in instrument
```

## Tracking Details
- **Project**: exercism-rails
- **Sentry**: [ActiveRecord::RecordNotUnique: Mysql2::Error: Duplicate entry 'github-39134240' for key 'users.index_users_on_provider_and_uid' (ActiveRecord::RecordNotUnique)](https://thalamus-ai.sentry.io/issues/95248537/)
- **Culprit**: Auth::OmniauthCallbacksController#github
- **First seen:** Feb 11, 2026