Improvement: support OAuth2 client credentials instead of ONLY authorization code flow

[nekman]

Thanks for a great plugin!

Instead of only allowing users to login with the Authorization code grant,
it is possible to login with client_credentials as well.

If you login using the example that you find under "My Applications" / "Your app":

curl -X POST -d "grant_type=client_credentials&client_id=<APP_ID>&client_secret=<APP_SECRET>" https://api.authentication.husqvarnagroup.dev/v1/oauth2/token

After you have logged in with your client credentials, you will get back a token for your own user (so it's important that the credentials is not shared) where you can control your Automower (if everything is paired and setup).

I think this will make it easier to setup everything for most users since the "My Home Assistant redirect feature" will no longer be needed.

For most users, the client_credentials should be enough (you typically use your own secret to login as your self and control your automower). For some edge cases, there might be other APIs and flows where authorization_grant is better if you want to allow other users to connect to "your backend" with their token (without sharing their passwords with that backend).

[Thomas55555]

Hi @nekman thanks for the idea.
Yes, you are right. A lot of people have to struggle with the Authorization code grant.
I think it was about one year ago. At this time the integration supported log-in with email and the client credentials. It was shortly before login with email/password was shutdown.
At this time I noticed it consumes a lot of time to support to authentication methods. And also at this time with the Application Credential platform it was easier to integrate Authorization code grant in HA. So I decided to use this method, as it seems to be the preferred method.