add Finna API connector

[ilkka-ollakka]

Description

Finna connector

Finna is finnish open API that contains among other things books released in finland

terms of use this API is located in https://www.kiwi.fi/display/Finna/Finna+API+Terms+of+Use and is CC0

more info https://www.finna.fi/Content/about_finnafi

Connector is heavily borrowed from openlibrary and inventaire codebase, this is my first PR toward bookwyrm codebase, so there might be somethings that I have fully missed.

• closes Add a connector to the Finna API #3147

Original thread where the idea started and people pitched ideas and approaches https://mementomori.social/@anotherdream/113881912359314786

What type of Pull Request is this?

• Bug Fix
• Enhancement
• Plumbing / Internals / Dependencies
• Refactor

Does this PR change settings or dependencies, or break something?

• This PR changes or adds default settings, configuration, or .env values
• This PR changes or adds dependencies
• This PR introduces other breaking changes

Details of breaking or configuration changes (if any of above checked)

Enables Finna connector

Documentation

• New or amended documentation will be required if this PR is merged
• I have created a matching pull request in the Documentation repository
• I intend to create a matching pull request in the Documentation repository after this PR is merged

Tests

• My changes do not need new tests
• All tests I have added are passing
• I have written tests but need help to make them pass
• I have not written tests and need help to write them

[ilkka-ollakka]

Fixed editions loading and picking edition from work so it prefers books over audiobook/ebook and finnish/swedish language ones if any found.

[ilkka-ollakka]

Fixed the issues that pylint/mypy/black complained, seems that I needed to add finna_key, so added it as separated first commit.

[ilkka-ollakka]

Cleaned out locale changes that jumped in by accident in some rebase