fix(deepl): Send payload in body, parametrize provider

This PR changes the deepl provider!

Description

Current DeepL map for language/translate is broken, basic request returns 400. It looks like DeepL stopped accepting payload in query parameters, and requires data to be passed in body.

Furthermore, it's not possible to use DeepL API Pro in current map, so I've added new SUBDOMAIN parameter. It defaults to api-free for the free API.

One caveat though: DeepL defines the following authentication schema in HTTP header:

Authorization: DeepL-Auth-Key [yourAuthKey]

However, we don't have any schema which allows formatting the Authorization header. Luckily the currently used scheme with auth_key query parameter works, but it's not documented and probably shouldn't be used.

Motivation and Context

Reported by user on Discord.

Types of changes

[x] Bug fix (non-breaking change which fixes an issue)
[ ] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

[x] I have read the CONTRIBUTING document.
[x] I haven't repeated the code. (DRY)
[x] I have added tests to cover my changes.
[x] All new and existing tests passed.

superfaceai / station