@roman.levinta you can use SQL wildcard symbol % for like search. You can query like below, which will return array of users for given criteria.
https://docs.camunda.org/manual/7.12/reference/rest/user/get-query/
Valid Queries are:
/engine-rest/user?firstNameLike=%ter&lastNameLike=Met%
/engine-rest/user?firstNameLike=Pe%er&lastNameLike=Met%r
/engine-rest/user?firstNameLike=%&lastNameLike=%eter
/engine-rest/user?firstNameLike=%ter
/engine-rest/user?lastNameLike=Met%
SQL Wildcard Characters:
| Wildcard | Description |
|---|---|
| % | A substitute for zero or more characters |