Add integration tests for pre-filled category/country at page with series creation after adding new category/country

[php-coder]

• After adding new category user should see a message with link to series creation page. When he/she open this link category must be filled
• After adding new country user should see a message with link to series creation page. When he/she open this link country must be filled
• When user open /series/add/category/{id} category must be filled
• When user open /series/add/country/{id} country must be filled
• When user open /series/add/category/{id} with unknown category, then category field must not be filled
• When user open /series/add/country/{id} with unknown country, then country field must not be filled

Technical debt for: 4877c26

[php-coder]

Because we don't have these tests we couldn't detect this regression: #438

[php-coder]

/series/add/country/{id} was replaced by /series/add/country/{slug} in 2886627 (#438)

[php-coder]

/series/add/category/{id} was replaced by /series/add/category/{slug} in 66ee8b4 (#206)

[php-coder]

/series/add/country/{slug} and /series/add/category/{slug} were replaced by /series/add?country={slug} and /series/add?category={slug} in e579d53 (#514)