[Update user profile] Verify that the system shows an error message when entering fewer than 2 or more than 50 characters in the "Username" field.

**Priority:**
Medium

**Preconditions**
1. User is logged in the system. .
2. The modal ‘Edit profile is opened.

**Steps to reproduce**
1. Enter 1 character in the Username field.
Expected Result: the system highlights the field in red and displays an error message:
EN: "This field must be between 2 and 50 characters."
UA: "Це поле повинно містити від 2 до 50 символів."
2. Attempt to enter more than 50 characters in the Username field (e.g. 51).

**Expected result**
1. The system does not allow entering more than 50 characters.
2. The system highlights the field in red and displays an error message:
EN: "This field must be between 2 and 50 characters."
UA: "Це поле повинно містити від 2 до 50 символів."

**User story:**#2078

**Related bug:**#2304