Description

This pull request updates the Javadoc of both RedisTemplate#keys() and RedisOperations#keys() methods to include a performance warning regarding the use of the KEYS command.

The KEYS command performs a full scan of the Redis keyspace, which can severely impact performance in production environments.
To avoid misuse, the updated Javadocs include a warning and recommend using scan(ScanOptions) as a safer alternative for large datasets.

• The warning has been added to:
  • RedisTemplate#keys() implementation method.
  • RedisOperations#keys() interface method.

Note: ReactiveRedisOperations#keys() already contains a similar warning and did not require changes.

Checklist

• I have read the Spring Data contribution guidelines.
• I used the code formatters provided here and did not include any formatting-only changes.
• No test cases were needed as this change is limited to documentation (Javadoc only).
• No author header update was required since only a Javadoc comment was changed and no logic was modified.

References

• Redis KEYS command
• scan(ScanOptions) alternative