Add tests for PostsController #create and #destroy

A magyar leírás lent található

## English description

The craete and destroy action of the PostsController have a small percentage of test coverage. We should implement request tests to improve this.

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## Magyar leírás

A PostsController create és destory action-jeinek kicsi a tesztlefedettésgége. Ezekhez kellene írni pár request tesztet.

Locate PostsController and review how its create and destroy actions are currently exercised. Follow the repository's existing request-test conventions, add coverage for both actions, and run the relevant request tests with coverage to confirm the gaps are addressed.

Written by the indexing model from the issue text.