[#noissue] Check existing users to handle duplicate user id error in insertUser()

[fatihsaracoglu]

Adding a Pinpoint user that has the same ID as one of the existing users throws database constraint violation error. It can be handled in the service layer.

The error shown on the UI:

### Error updating database. Cause: java.sql.SQLIntegrityConstraintViolationException: Duplicate entry 'test' for key 'puser.user_id_idx' ... ### SQL: INSERT INTO puser (user_id, name, department, phone_country_code, phonenumber, email) VALUES (?, ?, ?, ?, ?, ?) ### Cause: java.sql.SQLIntegrityConstraintViolationException: Duplicate entry 'test' for key 'puser.user_id_idx' ; Duplicate entry 'test' for key 'puser.user_id_idx'; nested exception is java.sql.SQLIntegrityConstraintViolationException: Duplicate entry 'test' for key 'puser.user_id_idx'

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