Allow Custom Headers

[Sherlouk]

Pull Request

Related issue

Fixes #290

What does this PR do?

• Adds a new parameter to initialiser to allow passing through of custom headers
• Custom header will not override API key which takes highest precedence
• Remove unused request parameter
• Remove unused header parameters in network functions

Though the public signature does change (for removal of 'request'), it was never possible to initialise your own Request due to no public initialiser being provided. As such it's impossible for any client to have this parameter in use, and thus this is not a breaking change.

PR checklist

Please check if your PR fulfills the following requirements:

• Does this PR fix an existing issue, or have you listed the changes applied in the PR description (and why they are needed)?
• Have you read the contributing guidelines?
• Have you made sure that the title is accurate and descriptive of the changes?

Thank you so much for contributing to Meilisearch!

[brunoocasali]

LGTM!

[Sherlouk]

bors merge

[meili-bors]

Build succeeded:

• integration-tests on macos-latest
• integration-tests on ubuntu-20.04
• linter-check