Add integration tests for the --header option

[theoforger]

Closes #3504.

Description

This PR adds the following two integration tests:

add_header

Use --header to add headers to:

• A request with no additional headers in the hurl file
• A request with some additional headers in the hurl file
• A request with a duplicate header in the hurl file

override_header

Use --header to override built-in headers: User-Agent, Accept, Host

[jcamiel]

/accept

[jcamiel]

Good job @theoforger !

[hurl-bot]

🕗 /accept is running, please wait for completion.

[hurl-bot]

✅ Pull request merged with fast forward by jcamiel..

# List of commits merged from theoforger/hurl/integration-test-for-header-option branch into Orange-OpenSource/hurl/master branch:

• ab29198 Add integration tests for the --header option