[CO#2, 3, 4, 5, 6, 7]Write unit tests for 'Додати вакансію' modal

[KateYatsiuk]

• test for creating a vacancy only with required fields
• test for creating a vacancy with all possible fields
• test for editing a vacancy
• check text amount restrictions in inputs
• check also functionality that when required fields are the same then existing vacancy should be updated instead of created

Component to put tests on:

Mock all needed requests as create, update, get vacancy