Need to localizate error message for non-unique username

[Flaurite]

Jmix version: 1.1.0-SNAPSHOT
Jmix Studio plugin version: 1.1.SNAPSHOT3217-211
IntelliJ version: IntelliJ IDEA 2021.1.3 (Community Edition)
run app>Application>Users>create
set username = admin
password = 1
Ok
AR:

QA

1. Create new single-module-project
2. messages file should contain the following key:
   databaseUniqueConstraintViolation.IDX_${userTable}_ON_USERNAME=A user with this name already exists
3. Try to reproduce the error. The localized message above should appear.

The same steps for single-module-application-kotlin.

[maistrenkoIulia]

please, change the message to
`A user with the same username already exists'