[crystal][client] Support authorization

[YusukeHosonuma]

Support authorization headers oauth2 and api_key.

• Update template files.
• Add unit test for api_client.cr. (#update_params_for_auth! only)

Note: Probably not the best, but I tried to make it work anyway.

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@wing328

[wing328]

CircleCI failure not related to this change.

[wing328]

LGTM. Thanks for the PR 👍

[YusukeHosonuma]

Thank you too for all your reviews 👍